The new service is now in beta and lets users post 140-character messages to an update screen that slowly scrolls old messages to the right of the chat window.
The service automatically links users with people on their Live Messenger contact lists, whose updates also appear on the scrolling timeline.
Posts are also stacked top-to-bottom and display only their first few words when they appear close together. Pointing the mouse at a condensed message shows its full version.
MSN China, the Microsoft joint venture that developed the new product, insisted it is not a microblog service.
"Juku is a local innovation developed by MSN China ... based on Windows Live Messenger networks," a company representative said.
But Juku, whose name uses the Chinese characters for 'gathering' and 'cool', is similar enough to a microblog site that one local media report called it a "bandit" version of Plurk, a Twitter-like service popular in Asia.
The Chinese term for "bandit" is slang for a product similar to that of an established brand and is most often used to describe knock-off mobile phones.
The new MSN service also lets users play simple games and earn prizes such as new face icons to post in messages. Users can upload a profile picture, visit the pages of other users and add them as friends.
Many Twitter-style services have appeared in China in recent months as social-networking sites grow increasingly popular.
About 124 million people, or one in three of China's internet users, currently use social-networking sites, according to the country's domain registry agency.
Micro-blogging in particular is also growing, though Twitter and some of its Chinese rivals have been blocked by the country's internet authorities for months.
Half of China's social-network users post microblog entries online at least once a day, according to the domain registry, though that figure likely includes messages similar to the status updates that can be sent on Facebook.
The new MSN service is likely an effort by Microsoft to win more users for its social-networking products as well as its instant-messaging service, said Ashley Liu, an analyst at In-Stat.
Windows Live Messenger is popular in China, especially among office workers, but rival instant-messaging program QQ is also widely used and has gotten a boost from value-added services built around it, Liu said.
Tencent, the owner of QQ, has had major success selling users upgrades to their accounts and virtual goods such as weapons for online games.
Users appear unable to buy virtual goods on the new MSN service. For now Microsoft may be foraying into social networking just to lower its dependence on its instant-messaging program in China, Liu said.
See also: Yahoo, Google on China porn list