Abstract: The method of constraints transformation based on local information is initiated for the structural supervisor synthesis of the discrete event system (DES) modeled by Petri nets. Specifications are described by constraints which may become illegal due to the uncontrollable or unobservable transitions. Forward-related structures of uncontrollable transitions and backward-related structures of unobservable transitions are analyzed separately, and local transitions can be used to realize the indirect control of the uncontrollable and unobservable transitions, which can transform illegal constraints into legal ones and still assure the original control specifications. Compared to matrix-based supervisor synthesis, the method of this paper needs only local information instead of global information. A real-world example is explained to describe the method.