The government believes the floating images of male and female police officers have proved successful during trials in the southern city of Shenzhen and will introduce them nationwide by the end of June, the official Xinhua news agency quoted public security officials as saying.
The introduction of the animated figures will be part of a campaign to weed out "harmful material and information" and "illicit activities" on the Internet.
Online gambling, pornography and fraud are among the top targets of the campaign, the agency quoted the ministry as saying.
"The existence of these problems has affected the healthy development of the Internet, brought harm to the youths' minds, contaminated the social ethos and disrupted the social order," it quoted vice-minister of public security Zhang Xinfeng as saying.
Problems include the "infiltration and spread of pornographic materials from abroad and lax domestic management of the Internet," Zhang said.
"The simple appearance of these floating icons will remind people these Web sites are under surveillance," the agency quoted government Internet expert Lu Benfu as saying.
Web sites in Shenzhen have been patrolled since last year by the uniformed Jingjing and Chacha, two smiling male and female cartoon figures who float astride surfboard-like keyboards.
The government tries to keep content on sensitive political and social issues broadly in line with the ruling Communist Party's ideology.
Tens of thousands of smaller Internet cafes have been closed, with the government favoring large chains that can be relied upon to monitor and control online activity among China's estimated 137 million Internet users.