In order to meet the demand of large scale boiler design and operating optimization, this paper establishes the dynamic mathematic model for domestic 600MW subcritical pressure boiler. MMS software is adopted in the whole process from modeling to simulation. This software make process simple and quick. This model is based on modulariza- tion and the comprehensive physical and chemical process in boiler is considered. Simulation result shows that the re- sponses of this model under different disturbance are coincident to mechanics analysis. The simulation result under ste Pdisturbance can be used to analyze unit changes and provide some guide and it also can supply performance reference data to boiler design.