The move is part of a broader state crackdown on spreading rumours and obscene material online, as well as attempts to rein in political commentary from media that has not been sanctioned by the state.
The man was taken into custody on Thursday after writing on WeChat that three people carrying explosives had been shot dead by police outside a hospital in the eastern province of Jiangsu, said a newspaper subsidiary of the official Xinhua news agency.
Police investigated the claim and found that it was untrue, the report said, adding that the man had confessed that he had spread the information to try and gain attention and boost his online business as an e-commerce merchant.
It was not immediately clear what sanctions he might face.
WeChat is a hugely popular mobile messaging app run by Tencent Holdings Ltd, which has already had dozens of widely read accounts run by outspoken columnists shut down in recent months as part of the state's Internet clampdown.
On Thursday, China imposed new regulations on instant messaging service providers and accounts that can send out mass messages to their followers, often used by media and companies. These require public accounts wishing to publish or reprint political news to seek prior approval.
WeChat was seen by users as a relatively safe refuge from government censorship compared to more public platforms such as Twitter-like microblogs, including Weibo Corp's Weibo.
Unlike Weibo, WeChat is primarily used to send messages to other individuals or small groups rather than large audiences.
But the rise of WeChat, which had nearly 400 million monthly active users by the end of March, has drawn government scrutiny, and with it greater regulation.
According to the rules announced on Thursday, public account users must sign an agreement when they register, promising "to comply with the law, the socialist system, the national interest, citizens' legal rights, public order, social moral customs, and authenticity of information".
In a commentary published on Friday, Xinhua said this was "a necessary step for a clean and healthy Internet".
"Instant messaging services have also been used by some people to spread content related to violence, terrorism, pornography and fraud," said Xinhua, adding that the new rules would "enhance the flow of content that people really need".
© Thomson Reuters 2014