It is necessary to manage room pressure strictly in order to prevent air flowing from outside for maintenance of products quality in clean rooms. A local exhaust system is installed in a special environment in which poisonous substances are handled to prevent the contamination. The reversal of pressure is not allowed under any situation as for such the special environment while usual air-conditioning operation is done. However, it is difficult to express room pressure changes of the air-conditioning system because present simulators do not have functions for expression of presser propagation. In this research, a dynamic simulator of pressure control with MATLAB is expanded in order to adapt to the more large-scale actual air-conditioning system. In addition, actual problems of the room pressure changes can be simulated successfully.