Abstract: Applications in heterogeneous networks could not communicate with each other directly because of the incompatibility of these protocols, so the integration of heterogeneous networks becomes difficult in network project. Protocol conversion is the key techniques in the interconnection of heterogeneous network system. The definition of protocol conversion is introduced, and the conventional methods of protocol conversion are briefly discussed in the paper,Following that, the definition of Petri net based protocol conversion is given. Then, taking advantage of the T invariant of Petri net and the parallel composition product, an algorithm of the construction of protocol convertor and its verification based on Petri net are proposed. At last, the feasibility of such algorithm is shown by an instance using this strategy of construction.