China's stock market has fallen by its biggest margin in eight years, defying Beijing's multibillion-dollar intervention to stop a slide that has wiped out the gains of this year's price boom.

Monday's decline threatened to weigh anew on global markets after last week's Chinese losses triggered a worldwide selloff.

The benchmark Shanghai Composite Index fell 8.5 percent, its biggest one-day loss since February 2007. The index was down 38 percent from its June 12 peak.

The slump has inflicted heavy losses on Chinese small investors, souring many on stock ownership and threatening to disrupt Communist Party plans to use the market to support reforms of state industry.

Pan Chong, a 25-year-old social media specialist who invested in April said, "It feels like the end of the world."