Zhuo, who stood by her late husband during the Cultural Revolution and his rise to power through economic reforms, died Wednesday in Beijing, the state-run Xinhua news agency reported.
An official memorial is set for Aug. 10 but mourners have been lining up in front of the couple's downtown Beijing residence, leaving bouquets to show their respect.
Zhou left instructions that her corneas and body are to be donated and that her ashes are to spread at sea like those of her husband, who died in 1997 at age 92, Xinhua reported.
Zhuo, a physicist, had been a consultant at the Central Military Commission General Office. She was raised in Southwest China's Yunnan province and became the first from her province to enroll in Peking University.
Zhuo said she chose physics because she believed only science could bring China out of its feudalistic past.
During the 1966-76 Cultural Revolution, Deng, who had been accused of being a "capitalist roader," and Zhuo were exiled in Jiangxi, where they worked in a tractor factory.