China has entered the emissions-cutting agreement reached last year in Paris in advance of the Group of 20 summit.
The state-run Xinhua News Agency reported that China's legislature had voted on Saturday to ratify the agreement.
Environmental groups expected China and the United States to announce they would adopt the Paris agreement, which calls on countries to set their own targets for reducing carbon dioxide emissions and update those targets every five years.
The agreement takes force when accepted by at least 55 countries that produce 55 per cent of global man-made emissions.
China and the US together produce 38 per cent.
