In order to keep multi-role communication action of virtual network classroom orderly and correctly at the same time, this paper proposes and studies its communication collaborative relationship based on Petri Net. Firstly, it introduces the basic theory and the system state change graph of the roles in virtual classroom, and discusses in detail the collaborative relationship between students and teacher in network environment. Especially by taking advantage of Petri Net tool, this paper in virtue of formalized method describes and analyzes collaborative relationship and collaborative mechanism between teacher and students, which exists in the virtual classroom. Finally, the collaborative mechanism has been realized successfully with the theory about process control concurrence view.