Units in river crossing operation can be easily exposed to fire attack of enemy so that they are vulnerable to the defeat in detail since they are split over the river. Thus, rapid completion of the operation is essential to preserve combat power and sustain the momentum of attack. However, there are not many endeavors to shorten the time of river crossing by improving tactical and operational methods. Hence, it is required to find improved operation methods of engineer river crossing equipment through validating the effectiveness of current tactic. In this research, we built a model that represent military operation of river crossing based on discrete event systems specification (DEVS) and simulated the operation to experiment operation methods with the model. We limited the river crossing operation to the operation of rafts of Ribbon Bridge System (RBS). Current operation methods are validated and more improved operation methods for rafts are suggested through this study.