While considerable effort has been dedicated to improve medical education with virtual reality based surgical simulators, relatively little attention is given to the simulation of the collaborative procedures in distributed environments. In this paper, we first present a literature review of techniques involved in the development of collaborative simulators, including network architecture, transmission protocol, collaboration mechanism, schedule algorithm, collaborative user-interaction feature and haptic communication. We introduce the details of each technique and discuss the advantages and drawbacks. Then, we review some of the existing applications to illustrate how to apply these techniques to implement an efficient and robust collaborative simulator. Finally, we discuss the challenges that need to be addressed in the future.