Winning a gold medal at the Olympics should be one of the happiest moments of an athlete's life.

But that was not the case for Chinese diver Wu Minxia.

After winning the women's synchronized three-metre springboard competition in London on Sunday, the 26-year-old Olympian got devastating news: her family decided it was the right time to tell her that her grandparents had died - over a year ago - and her mother had breast cancer for eight years, AFP reported.

Wu had no idea. Her father admitted the news was kept from her to avoid any distractions during her quest for gold.

"Wu called us after her grandmother died, I gritted my teeth and told her: 'Everything's fine, there aren't any problems'," father Wu Jueming told the Shanghai Morning Post.

"It was essential to tell this white lie. We never talk about family matters with our daughter."

Her mother defended the decision, saying she waited until her cancer was in remission before telling Wu.

The story of the Wu family's secrets has added to a public "backlash against the win-at-all-costs mentally" in China.

Thousands of Chinese web users took to Sina Weibo - a Chinese microblog similar to Twitter - to condemn what they say is an example of the harshness of China's government-funded sport system, AFP reported.

"Apart from making people crazy, our Olympic strategy also makes people lose their humanity," one online commentator said.

"Our national sports system is disgusting," another said.

Wu, who with teammate He Zi won the synchronised gold medals at the Olympics in Athens and Beijing, was a favourite to win again this year.

She began drive training when she was six, and left home at 16 to focus on her career.

Wu Jueming told the Shanghai Morning Post he hardly saw his daughter, keeping track of her activities by following her blog.

"We've only sent our daughter one text message since we arrived in London, to tell here we are safe, so she wouldn't worry," he said.

"She doesn't call us often because she's busy with training.

"We've known for years that our daughter doesn't belong to us any more."

- © Fairfax NZ News