Based on the physical processes of regenerative heating systems, the mathematical models of regenerative system,reheat system and steam turbine for a 200MW reheating steam turbine are presented, and the digital simulation of them on IBM-PC is also provided in this paper. The present work is a part of the study of the dynamic characteristics of all power systems. The mathematical model is expressed into state space form ,and its matrix is standardized to avoid the repeatation of establishing the models of heat exchangers.