Mobile phone users represent a large share of the online population, the centre said, with 527 million people in China accessing the Internet using mobile devices in the six months to June.
But even as the number of users of services such as online games, banking and shopping continued to rise, use of social networks declined, the report said.
According to CNNIC, 257 million people used social networking sites during the period, down from 278 million in its last set of figures in December -- a 7.4 % drop.
The fall coincides with a crackdown over the past year on social media sites such as Sina Weibo, a Chinese Twitter equivalent, and Tencent's WeChat, an instant messaging platform that allows users to send text, photos, videos and voice messages over mobile devices.
China already had more web users than any other country in the world. It is home to a huge e-commerce market and the web has been used by citizens to spotlight government abuses, creating a concern for the ruling Communist Party.
Beijing maintains tight controls over the Internet, blocking websites it deems politically sensitive in a system dubbed the "Great Firewall of China" and obliging social media companies to censor user-generated content.