The petition would be a mainly symbolic gesture to the legal authorities that last year convicted Wang in a trial lasting only four hours, said his mother Wang Lingyun.
"There is no optimism over the result," she said in a telephone interview. "This is an expression of our attitude."
Wang's family had already prepared documents for the petition, which they expected to submit to the Peking Higher People's Court later this month, she said. "In accordance with the legal system, after Wang Dan's appeal, he himself or his family are allowed to submit a petition," said the 61-year-old museum researcher, who helped to defend her son during his trial last year.
"I've written a first draft but I haven't sent it yet," she said. "I need to tidy it up before submitting it to the court."
Chinese legal experts say that submitting petitions to overturn verdicts which have already survived an appeal have almost no chance of succeeding in forcing a retrial.
Wang Dan was one of the leaders of the pro-democracy student protests of 1989 that were crushed by the Chinese army with heavy loss of life. He was sentenced last October.