The Independent reported Sunday that the woman, Cheng Jianping, was sentenced to a year in a labour camp for re-posting a Tweet from her fiancé.
Twitter's chief executive, Dick Costolo, posted a message that read: "Dear Chinese Government, year-long detentions for sending a sarcastic Tweet is neither the way forward nor the future of your great people."
Twitter is blocked in China, but some rights activists have managed to bypass the controls.
Hua Chunhui, Cheng's fiance, said the original Tweet was on recent anti-Japanese protests in China.
It read: "Anti-Japanese demonstrations, smashing Japanese products, that was all done years ago by Guo Quan (an activist and expert on the 1937 Nanking Massacre). It's no new trick. If you really wanted to kick it up a notch, you'd immediately fly to Shanghai to smash the Japanese expo pavilion."
Cheng re-posted this and added: "Angry youth, charge!"
Cheng had earlier put out a message supporting Liu Xiaobo, the jailed pro-democracy campaigner who has been awarded the Nobel Peace Prize.
Hua said Cheng arrived at a labour re-education centre in central China's Henan Province Wednesday.