There are more net users in China than US citizens
Google says it will take "all necessary steps" to remove pornography from its Chinese language portal, Google.cn
The firm was responding to criticism from China's internet watchdog which said Google was "disseminating pornographic and vulgar information".
Google has been warned twice about allowing unacceptable porn sites to be seen in search results.
The news comes as China tries to make sure all new PCs sold in the country are fitted with filtering software.
A popular outcry over the PC filtering plan prompted the Chinese government to clarify that, although the surveillance software will ship with every computer, it does not have to be used.
The Chinese government said its crackdown on Google - and other major websites - was to tackle the "large volume of foreign internet pornographic information [that] has entered our borders".
Google responded in a statement, saying it had met with government officials to discuss issues surrounding its Google.cn service.
"We are undertaking a thorough review of our service and taking all necessary steps to fix any problems with our results," said Google's communications director, John Pinette, in a statement.
China's Internet Illegal Information Reporting Centre (CIIRC) said further action may be taken.
According to the CIIRC, 1001 websites were blocked by authorities for "distributing porn and other lewd material" and more than 4,000 other sites were also closed.
At the end of 2008, the number of net users in China, which has a population of 1.3 billion, was almost the same as the entire population of the United States.