This paper discussed the relationship between biological control of pests and conservation of biodiversity, pointing out that biodiversity was the source of biological control agents, and in turn biological control of pests played an important role in conservation of biodiversity. It reported briefly the diversity of natural enemies and their host specificity in natural and agricultural ecosystem, and the roles of biological control in management of exotic species as well as conservation of endangered species and habitats. The authors also emphasized that international exchange of natural enemy resources should be widely supported and the code of conduct for the import and release of biological control agents should be earlier established in order to implement more safe and effective biological control programs.