A court in the eastern city of Hangzhou on Monday convicted Huang Dingfang and Cai Keyi of fraud, Xinhua news agency said.
Hang set up Longyan E-commerce Co. Ltd. in January 2015 and worked with another company owned by Cai to cheat the investors out of 15.6 billion yuan, the court said.
They promised annual returns of more than 250 percent if investors became members by paying 4,000 yuan each and then bought shares.
The pair also set up a third firm to sell shares and promised that the company would go public in the United States, Xinhua said.
Ding Wenping, chief financial officer of Longyan E-commerce, and Sun Shijia, its president, were jailed for 12 and 10 years respectively.
Seventeen others were given sentences of up to nine years.
The court also ordered the 21 defendants to return 5.7 billion yuan to more than 170,000 investors.