In this paper the development of simulation technologies and modeling theory of the fossil power generating unit in China is discussed and analysed. Authors described developing process of the fossil power simulators from scientific researches to achieving the most quantity in the world. While the information of electric power simulators distributed over the world is given. The key technologies——modeling theory and method of the thermal system simulation are summarized. Authors expounded the lumped parameter model, distributed parameter model, dynamic revised model of high precision lumped parameter and other model. These model equations are applied various simulated objects and different simulation precision.