Zhao Ziyang's family told relatives and friends in a text message that Liang Boqi died peacefully at Beijing Hospital on Wednesday night. The cause of death was not disclosed.
Zhao helped promote reforms that launched China's economic boom but was purged after he called for compromise and expressed sympathy for some of the students' demands during the 1989 protests.
He was accused of splitting the party and placed under house arrest after the military crushed the protests. Liang, who married Zhao in the 1940s, accompanied Zhao in his 16 years of house arrest until he died in 2005 at age 85.
Chinese scholar and family friend Wu Jiaxiang said he was among those who received the text message. Hong Kong-based book publisher Bao Pu, one of the editors of Zhao's secretly compiled posthumous memoir "Prisoner of the State," also confirmed that he had received a notice announcing Liang's death from at least two relatives of Zhao.
Bao Tong, Zhao's former secretary, said Liang had been in poor health in her final years and dependent on her caregivers.
State media did not carry Liang's death notice on Thursday, but the news was circulating in China's social media, where people lit virtual candles to express condolences and reflected on Zhao's political and economic contributions.
"It is a huge regret that she did not live to see the day that Zhao's reputation is restored," the scholar, Wu, said. "She didn't get to wait for that day to come."