Only 12 people survived the disaster on the night of June 1, Tang Guanjun, director of the Yangtze River Navigation Affairs Administration, told a press briefing.
Earlier 456 people were reported onboard the cruise ship and 14 survived.
Tang explained that the final revisions were made after further check-ups and verifications, state-run Xinhua news agency reported.
He said rescuers from different agencies made repeated calculations of the number of survivors.
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Rescue and search operations have ended, but investigation is still under way, he said.
The Eastern Star was on an 11-day trip along the mighty Yangtze river with 456 people onboard when it capsized during a storm on June 1.
The 76.5-meter vessel had been in service for nearly 20 years and can carry up to 534 people, the report said.
The tragedy was China's worst shipping disaster since the Communist Party came to power in 1949.