The International Energy Agency says China overtook the United States in 2007 to become the world's top carbon emitter.
The IEA revealed the figures at a UN climate change meeting in Bangkok on Tuesday.
It said China emitted 6 billion 71 million tons of carbon dioxide emissions in 2007, or 21 percent of the global total. The United States produced 5 billion 769 million tons, or 19.9 percent, falling behind China.
The IEA said China will have to increase its use of nuclear and wind power energy by 16 percent.
It said China will also need to promote energy efficiency and reduce its emissions to GDP ratio.
The agency said China can reduce its emissions by about one billion tons, or more than 10 percent, in 2020 if these actions are taken.
IEA Executive Director Nobuo Tanaka said China has an important role to play in the global reduction of greenhouse gas emissions.
He added that it is essential for the industrialized countries to offer technology and financial support to help China cut its emissions.