Abstract: The protection of biological diversity is not only to safeguard the wild species, but also to conserve the clutivatedand domesticated ones. The animal and plant quarantine plays an important role both in safeguarding the cultivatedand domesticated species and in preventing their outflow. It should be recognized that the animal and plant quaran-tine system is actively involoved in the protection of biological diversity. The author emphasized that firstly, it isnecessary to strengthen the animal and plant quarantine system so as to reduce the effect of international trade onbiological diversity, secondly, to intensify the quarantine safegurd on ports of entry to protect the endangered andrare species. Examples are giveti to illustrate the destruction and loss of rare biological resources resulted from thespecies out flow in international trade in the past years, and reviewed the role of animal and plant quarantine instrengthening the management of endangered and rare species.