The campaign will last until November, state-run Xinhua news agency reported.
All online texts, pictures, videos and advertisements with pornographic content will be deleted, according to the circular.
Websites, web channels and columns will be shut down or have their administrative license revoked if they are found to produce or spread pornographic information, it said.
Websites, telecom operators and web portals were asked to conduct a self-examination instantly and clean up information and links.
The campaign is in response to the persistent spread of pornography online despite multiple previous campaigns.