Liu Xia warned in an open letter posted on her lawyer's Twitter account -- days after her brother was sentenced to 11 years in prison -- that rights violations jeopardised Xi Jinping's recent calls for a national renaissance.
"Don't let the Chinese Dream for people like us become a 'Chinese nightmare'," she wrote.
"What we should see from national authorities is justice, not merciless oppression."
Liu's lawyer Shang Baojun confirmed to AFP that the message was written by Liu.
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Her husband, the political activist Liu Xiaobo, was jailed for 11 years in 2009 for "subversion" after he circulated a charter calling for democratic reforms.
He became China's first Nobel Peace Prize winner in 2010, angering Beijing, and for the past three years she has endured strict surveillance.
China's ruling Communist Party keeps a tight grip on power, dealing harshly with dissidents and other potential threats to its authority.
"I have lost all of my personal freedom," she wrote.
"Perhaps in this country being the wife of Liu Xiaobo is a kind of crime."
On Sunday her brother Liu Hui was sentenced to 11 years in prison for fraud in connection with a real-estate deal. He had been detained in January.
Liu Xia was allowed to make two rare public appearances to attend the trial, once in April for the opening session and again this week.
In her letter she called the verdict on her brother "totally unfair".