The passive residual heat removal system (RHRS) is an important safety system for the HTR-PM reactor. Due to the thermo-dynamic coupling between the reactor core and the passive RHRS, an overlapping domain decomposition coupling method is employed for the analysis of the operating characteristics of the passive RHRS of the HTR-PM. The software TINTE-RHRS is developed based on this methodology and is used for the coupling calculation, and an integration solution can be obtained for both the primary system and the passive RHRS. The system models are also presented in this paper. The thermal-hydraulic characteristics of the passive RHRS in the pressurized loss of a forced cooling (PLOFC) accident are simulated using the TINTE-RHRS code. The importance of the coupling calculation between the primary system and the passive RHRS is shown; and the effects of the number of operating systems and the air temperature on the operating performance for the passive RHRS are also addressed.