The chemical plant is a typical example of a combined continuous-process and discrete-event system. In this paper, a new method which can fulfill the functions necessary to achieve a combined continuous-process and discrete-event simulation is explained. The activities for plant operation are usually described by two types of models, i.e., continuous process and discrete event. However, it is more convenient to deal with the sequential control model as the third element since it contains an intermediate property between the discrete event and continuous process models. The simulation program provides the users many standard elements to build their customized models and a function of connecting these three models for total system simulation. It can be applied to a complicated plant operation system such as combined batch and continuous process plants, pipeless batch process plants, and textile mills.