China's Premier Li Keqiang unveiled a lower growth target and pledged tighter environmental controls as he opened parliament's annual session.
Addressing the National People's Congress (NPC), Mr Li said China would target growth of about 7% in 2015.
With traditional drivers of growth weakening, more structural reform was needed going forward, he said.
Describing pollution as a "blight" on quality of life, he said environmental laws would be strictly enforced.
Some 3,000 legislators from across China convene for the annual legislative session at Beijing's Great Hall of the People.
China describes the NPC as the "supreme organ of state power". It has the power to enact and amend legislation. In practice, it is generally considered a rubber stamp for the ruling Communist Party.
The premier's work report traditionally opens the session, which ends on 15 March.
Analysis: Celia Hatton, Beijing
Every year, the Chinese premier's annual work report skims a wide variety of topics. The speech is supposed to function as a grand overview of the government's triumphs and failures in the past year, while also signalling Beijing's future priorities.
This year showed a narrowed focus on two major topics: the economy and the environment.
Thirty pages of Li Keqiang's 38-page speech were devoted to the slowing economy. He used the now-ubiquitous phrase the "new normal" to reassure his audience that a lower GDP forecast of 7% was natural and would be in place for a few years.
But the most heartfelt language focused on environmental pollution, an issue that Li Keqiang acknowledged was "a blight on people's quality of life and a trouble that weighs on their hearts". A long list of promises followed, from forest protection to the promotion of electric vehicles.
On both issues, Mr Li attempted to strike the same tone: he wanted to appear in touch with problems on the ground and the frustrations of the Chinese people, while reassuring the public that his government knows how to tackle the problems.
Announcing the annual growth target, Mr Li said China had to "maintain a proper balance between ensuring steady growth and making structural adjustments".
The 7% figure is lower than the 7.5% set last year - a target that was missed as China grew at its slowest pace in 24 years.
After years of double-digit growth, China's leaders are now advocating a "new normal" of slower expansion.
The world's second largest economy is trying to move from an export-led growth model fuelled by government investment to one driven by higher domestic consumption and a larger services sector.
"Deep-seated problems in the country's economic development are becoming more obvious," said Mr Li.
"The difficulties we are facing this year could be bigger than last year. The new year is a crucial year for deepening all-round reforms."
He said China aimed to create more than 10 million new urban jobs in 2015 and maintain an unemployment rate of 4.5%.
Job creation is seen as vital to providing employment for the millions of new graduates who emerge on to the job market each year.
On the environment, Mr Li promised to fight pollution "with all our might".
"We must strictly enforce environmental laws and regulations; crack down on those guilty of creating illegal emissions and ensure they pay a heavy price for such offences," he said.
China is facing major pollution problems after runaway industrialisation. Last year, a government report found almost a fifth of China's soil was contaminated. Unhealthy levels of smog frequently hit its major cities.
Mr Li touched on corruption only briefly, telling lawmakers that the "tough stance" was here to stay.
The government also confirmed that the military budget would rise 10.1% in 2015, as indicated on Wednesday by an official.