In his first news conference, Mr. Li said on Sunday that China will rely on the continued migration of its people to cities to boost domestic consumption, and so remake the country's economy into one less dependent on investment spending at home and exports abroad.
His predecessor, Wen Jiabao, had offered similar projections, only to make little progress in this "rebalancing" of the economy.
The 57-year-old Mr. Li also said the government should give markets greater room to operate, including allowing private businesses to compete on an equal footing with state-owned enterprises. In finance, the market would play a greater role in setting interest rates and the exchange rate, and companies would have greater access to funding through the bond and equity markets, he said.
"Talking the talk is not as good as walking the walk," he said. "We need to pursue market-oriented reforms."
The premier's annual news conference is the only time the Chinese public gets to see the leader who steers the world's second largest economy being quizzed by the media, even if the questions and answers are mostly scripted.
Mr. Wen had sought to portray an avuncular man-of-the-people image, although he had a somewhat stiff manner on the podium. Mr. Li has a more informal style, and a down-to-earth delivery that resonated on China's social networks, where many noted his absence of official airs.
His promise to cut back on the expenses of officials was widely hailed by a public angered by government extravagance.
On Sunday, Mr. Li was flanked by his lineup of vice premiers, who sat wordless throughout the event.
In response to a question about his personal experiences, Mr. Li recalled that he was sent to the countryside to do manual labor like many young people during the Cultural Revolution.
"It is the reform and opening-up policy that changed our country's fate," he said. "I don't have more time to talk about my personal experiences.…I firmly believe that you can only benefit your country by being honest, and being fair and just in handling affairs."
Mr. Li's remarks came a day after the country's cabinet was approved by the rubber-stamp Parliament, the National People's Congress. Zhou Xiaochuan, already China's longest-serving central banker, was reappointed—even though in January he turned 65 years old, the usual retirement age for ministerial-level positions like governor of the People's Bank of China.
The reappointment was widely seen as a signal of Beijing's desire to stay on course with the kind of financial reforms championed by Mr. Zhou, including a more flexible Chinese currency. But some analysts expressed concern that it also reflects a continuing failure in China's development of a rules-based government.
"It's positive in the sense that the new leadership is sensible—keeping someone who is capable and respected," said Minxin Pei, a China specialist at Claremont McKenna College. "It's negative because it shows that rules do not mean much."
China also anointed Lou Jiwei, currently chairman of the country's giant sovereign-wealth fund, as finance minister; Xu Shaoshi, currently minister of land and resources, will be head of the National Development and Reform Commission, the country's top economic planning agency.
These appointments are part of a broad shuffle of government posts under the new leadership headed by Mr. Li and Communist Party chief Xi Jinping, who was also ratified by the NPC as the country's president.
While all the officials named have some reputation as reformists, their appointments reflect politics perhaps more than policy preferences. Top Communist Party leaders have been engaged in behind-the-scenes discussions for months about filling top government jobs.
Zhang Gaoli—a member of the Communist Party's seven-man Political Standing Committee, its top decision-making body—became first-ranking vice premier and an influential figure on the new economic team.
Liu Yandong, Ma Kai and Wang Yang were also named as vice premiers.
Mr. Wang, who has a relatively liberal record of economic and political change as the party chief of southern Guangdong province, didn't get a Standing Committee slot but is expected to play an important role on the economic team. It remains unclear whether he will be in charge of finance, industry or agriculture.
Mr. Xi used his first speech as state president, at the closing ceremony of the Parliament meeting, to make the latest in a series of appeals for the country to pursue the "China Dream"—the signature slogan of his leadership so far.
He paid tribute to his predecessor, Hu Jintao, praising his "rich political wisdom, skilled leadership capabilities and diligence."
But he also differentiated himself from Mr. Hu by outlining a more muscular vision of China's future, stressing the "dream" of national rejuvenation, and urging the military to be ready to "fight and win battles."
A visit to Beijing on Tuesday by U.S. Treasury Secretary Jacob Lew should clarify which of the officials, aside from Messrs. Xi and Li, will play important policy roles on international economic issues. Those will be the officials Beijing makes available to meet with Mr. Lew.
Mr. Li pledged no further spending on central government buildings, and promised to crack down on foreign travel, entertainment and car purchases by officials, echoing the theme of austerity pushed by President Xi in response to endemic corruption that is eating away at Communist Party credibility.
He told officials they shouldn't expect to get rich through government work.
"Pursuing government office and making money have been 'two separate lanes' since the ancient times," Mr. Li said.
—Tom Orlik and Jeremy Page contributed to this article.