Abstract: The simulation model built by reactor transient calculation program RELAP5-HD is mainly expressed by partial different equation, which could be applied for the simulation and verification of coolant temperature system. However it is difficult to optimize the controller design of coolant temperature system because the developed control theory could not analyze the stability, steady-state characteristics and dynamic characteristics of the system directly based on partial different equation. In this paper, a transfer function model of lead-based cooled fast reactor thermal-hydraulic system severing for coolant system characteristics analysis was built based on the first principle of thermal-hydraulic and the method of spatial discretization. The contrastive simulation result of the model and RELAP5-HD model indicates that while the control variable step changing, the output characteristic of transfer function model is quite similar to the RELAP5-HD model, reflecting the system dynamic characteristics accurately, and the control theory could be applied in the characteristic analysis study of lead-based cooled fast reactor coolant temperature system.