Abstract: In order to solve the Problem of structure analysis for Colored Petri nets (CPN) in large complex system engineering applications, a kind of unfolding approach for CPN is proposed. Based on the proposition logic represented with the Petri Nets, the semantics of the CPN SML (Standard Meta Language) are discussed. After that, the unfolding approach of CPN is proposed including the steps and unfolding algorithm based on the semantics verification. And the approach is exemplified on the programmed operation platform, which approves the approach is feasible and e ective to to make the CPN strucure analysis widely used in complex engieering models.