China's National People's Congress voted to adopt "the proposal to review and ratify the Paris Agreement", the official Xinhua news agency said.
The agreement, announced with great fanfare at the Cop21 climate talks in Paris at the end of last year, calls for capping global warming at well below 2.0°C and 1.5°C if possible, compared with pre-industrial levels.
China is responsible for around 25 percent of global carbon emissions, with the US in second place on about 15 percent.
Only 24 of 180 have signed
The Paris deal will come into force 30 days after at least 55 countries, accounting for 55 percent of global greenhouse gas emissions, have ratified it, but until Saturday only 24 of the 180 signatories had ratified it, with France being the only European country to do so.
The agreement is "far from certain" to come into operation before the end of the year, French President François Hollande warned recently, calling on countries to "turn promises into action".
The Institute of Climate Analytics has listed 34 countries, including Brazil, Indonesia, Japan and Iran, have pledged to ratify this year.
To read our coverage of the Paris Cop21 climate change conference click here