Sun, the 5,000m bronze medallist at the 2003 World Championships who is currently serving a two-year ban for doping, said coach Wang Dexian subjected her to frequent scoldings and would whip her with a belt..
"My back is covered with so many cuts and bruises that I can not even take off my clothes," she said in a TV interview, according to the China Daily newspaper.
The alleged abuse came to a head recently when she was whipped with a belt after a difference of opinion with Wang's wife, Zhu Fengling, also an athletics coach.
"He beat me with a belt after I contradicted his wife. It was the most ruthless (attack) since I started training with him 10 years ago," Sun, 27, was quoted as saying.
"My back hurt so much, I could not tolerate it."
Sun has since ended her partnership with Wang and is now training alone in a bid to make a comeback for the 2008 Olympics in Beijing.
The runner returned a positive dope test at the National Games in October last year, and was banned from international sport until October 19, 2007.
However, in December last year Sun won a court case against fellow athlete Yu Haijiang, whom she accused of spiking her drinks, causing her to fail the doping test.
Despite this, the sprinter was stripped of her 10,000m title at the National Games and thrown out of the tournament, a key event prior to the 2008 Olympics.
Wang declined to respond to the allegations of abuse levelled by Sun, but his wife confirmed that he had split with the athlete in August.
A lawyer for Wang told the China Daily that he had not ruled out taking legal action against the runner for libel.