By Peter Feuilherade
"Unhealthy" content should be purged from the net and replaced with Communist doctrine, China President Hu Jintao was reported as saying.
Many Chinese people access the net in cafes
President Hu was speaking at a meeting of the Communist Party Politburo, which pledged to impose firmer propaganda controls on the net.
The move is the latest in a series of crackdowns on China's estimated 137 million net users.
In January President Hu said officials must nurture a healthy online culture.
"Development and administration of internet culture must stick to the direction of socialist advanced culture, and adhere to correct propaganda guidance," the Politburo meeting resolved, reported China Central Television (CCTV).
During the last week, a campaign in China's media has highlighted the negative impact of indecent internet content.
CCTV has broadcast daily reports showing students and their parents protesting about the harm such content caused.
The number of internet users in China grew by almost 24% last year and now one tenth of the population is thought to be online.
The drive to clean up the internet follows directives earlier this year aimed at "purifying" television broadcasts, including demands that stations reserve prime-time slots for "ethically inspiring TV dramas" and clampdowns on talent shows.
The steps are seen by some as signs the party is tightening its grip on information dissemination before its sensitive 17th congress.
The congress is expected to be held in October and will see major leadership changes," the Hong Kong newspaper South China Morning Post reported on Tuesday.