Abstract: A method for modeling a Discrete Event System includes the steps of: a) receiving the user-defined requirement and specification of a Discrete Event System; b) extracting events and action from the user-defined requirement and specification and storing the events and action; c) generating a tree-type data structure including start node; d) searching the stored events to determine existence of allowable events from the event represented by a leaf node. which quits the generation of the tree-type data structure when there is no allowable event; e) when there is the allowable event in the stored events, generating a child node of the leaf node, the child node representing to allowable event and F) iterating the step of searching and the step of generating a child node for all the leaf nodes of the tree-type data structure.