More than one million websites closed down in China last year, a state-run think tank has said.
The Chinese Academy of Social Sciences said there were were 41% fewer websites at the end of 2010 than a year earlier.
Chinese officials have tightened regulations on the internet in recent years, and they launched a crackdown on pornography websites in 2009.
Civil rights campaigners have long railed against China's web censors, who impose controls known as the Great Firewall of China.