An estimated 60 per cent of North Korean girls and women in China are trafficked into sex trade, according to the report, launched at an event at Britain's Parliament.
Nearly half are pressed into prostitution, pushed into cybersex, researchers said.
No one at the Chinese embassy in London was immediately available for comment. Gathering information in North Korea is notoriously difficult.
Many North Koreans are enslaved in brothels in districts in the east China with large migrant worker populations, the report said.
Trafficking survivors said prostitutes further south, in Shanghai, they were branded with tattoos such as lions and butterflies to show ownership and deter abductions by rivals.
Interviewees told of women dying from sexually transmitted diseases and abuse.
Girls and women enslaved in cybersex are usually aged between 12 and 29 but are younger, the report said.
Sex acts or sexually assaulted in front of webcams. A live-stream featuring a young girl can cost $ 110, researchers said, adding that many subscribers appeared to be South Korean.
One woman, referred to as Ms Choi, told how to take an apartment where she was shocked to see pre-pubescent girls.
"[There] was a bed in front of the computer. Four men … gang raped me. When the third man started raping me [I] was bleeding … I cannot remember any more."
The report said women were married in rural areas for 1,000 to 50,000 yuan, and were raped and abused by their husbands.
Estimates of the number of North Koreans in China vary between 50,000 and 200,000. Yoon said, China's policy of detaining and repatriating North Koreans forces to live in the shadows, placing them at high risk of exploitation.
Some are sold by policemen after arrest, while others are duped by traffickers offering to countries where they can claim asylum, the report said. Abductions are also common.
Researchers said stretched into North Korea where "sub-brokers" scour markets, villages and transport hubs for destitute-looking girls to fulfill orders from Chinese pimps and madams.
David Alton, co-chairman of Britain's All-Party Parliamentary Group on North Korea, said the abuse by the two-year investigation was "horrific".
He said the trafficking of North Korean women was tied to China's one-child policy, which has distorted the country's gender balance two to the preference for boys.
One trafficking survivor, who had repatriated three times before finally escaping to South Korea, were forced to undergo abortions.
The woman said she was in a concentration camp where her doctor was born – without anesthetic – and tore him limb from limb.
The London-based Korea Future Initiative urged all countries to help North Koreans in China escape and said embassies should accept asylum seekers as refugees.
Thomson Reuters Foundation