Hu said Henan authorities had warned Gao not to attend the Vital Voices Global Partnership awards ceremony next month in Washington but she refused to comply.
He said Zhengzhou city authorities put her under house arrest.
Her daughter is under constant police surveillance.
Local officials have refused to comment on the case.
Hu said Gao was to be honoured for her work promoting women's legal rights in China.
Gao had once before been refused a passport in 2001 to go to Washington to accept an award from a United Nations group.
In the late 1990s, she alerted people in her eastern home province of Henan about an Aids outbreak being spread by tainted blood transfusions, efforts which earned her numerous awards.
Health officials had accused her of helping "anti-China forces" by speaking openly to the press and distributing brochures about the spread of the disease among poor farmers due to the selling of tainted blood.
Chinese leaders have since become more open in confronting the disease, promising anonymous testing, free treatment for the poor, and a ban on blood sales and discrimination against people with the virus.
But Aids workers still face frequent harassment by local authorities who fear their activism will reflect badly on them, possibly jeopardising their jobs or chances for advancement.
Gao's activism began in 1996 when she wrote and printed copies of a basic Aids information pamphlet for distribution at Zhengzhou's long-distance bus stations.
Since then, she has distributed medicine, cared for orphans of parents who had died from Aids, written a book about China's epidemic and hosted patients in her modest apartment.