Abstract: To deal with modeling of hybrid system, a sort of hybrid Petri nets named hybrid state Petri net(HSPN) is proposed, with its definitions and transition rules. As an example, a practical chemical process is given, and its HSPN model, which can be used to construct a hybrid controller, is built up. Simulation indicates that this HSPN model is effective. Some properties of HSPN are also briefly investigated.