Mr Wen's attendance "will fully demonstrate the great importance the Chinese government attaches to this issue, as well as the political will of the Chinese government to cooperate with the international community," spokesman Qin Gang said at a news briefing.
Also on Thursday, China’s State Council announced plans "to reduce the intensity of carbon dioxide emissions per unit" of gross domestic product in 2020 by 40 percent to 45 percent, compared with its 2005 level.
The reductions will be "based on our own national conditions" and "is a major contribution to the global effort in tackling climate change," the State Council said, according to the Xinhua news agency.
The news followed US President Barack Obama’s announcement Wednesday that he would attend the summit, which is to run from December 7 to 18 in Copenhagen.
The executive secretary of the climate change conference welcomed the announcements from China and the United States but called for rich countries to come up with money to help poor countries meet their goals.
Next month's climate talks aim to strike a deal on a successor agreement to the Kyoto Protocol, the 1997 pact that has legally binding targets for reducing greenhouse gas emissions. The United States never ratified it, though more than 200 nations did.