Angola has deported 37 Chinese nationals, accused of extortion, kidnappings, armed robberies and running prostitution rings.
They are accused of targeting other Chinese, kidnapping businessmen for ransom and sometimes burying their victims alive.
Chinese police said women were lured to Angola, promised well-paid jobs and then forced into prostitution.
A special police team was sent from China to Angola in July to help investigate criminal gangs.
The Ministry of Public Security said the officers helped their Angola to break 12 gangs and free 14 people.
The BBC reports the 37 suspects arrived at Beijing airport in handcuffs with balaclavas covering their faces. They are to be tried in China.
Angola is China's biggest trading partner in Africa, worth $US24.8 billion in 2010. But crime has begun to seriously affect operations there.