The Chinese authorities say they have shut down nearly 700 websites and arrested 224 people in a new campaign against internet pornography.
Chinese authorities have an ambiguous attitude towards the web
The campaign, launched about two weeks ago, requires internet providers to register users under their real names.
New technology has also been introduced to block porn websites based overseas.
The state-run Xinhua news agency says the growth of such sites may result in a decline in ethical standards among young people.
"Existing and developing technology should be sufficient to ensure the Chinese government's triumph in its campaign," the agency quoted an unnamed official as saying.
It is estimated that 87 million people in China use the internet, half of them under the age of 24.
Many visit porn sites to learn about sex as the subject is seldom discussed with parents, Shanghai student He Tao told AFP news agency.
"Porn websites are rooted in young people who are thirsty for the facts of life, on which education is so deficient," he said.
China's authorities have shown an ambiguous attitude to the rise of internet use.
On the one hand they see it as essential for the economy to have a computer literate population.
But on the other hand they have sought to restrict use of the internet for political purposes.
Beijing has blocked access to dissident websites and most foreign news organisations.