Different from most current commercial nuclear power plants, the High-Temperature gas-cooled Reactor Pebble-bed Module (HTR-PM) power plant consists of two reactor modules connected to a common steam turbine system that will bring a special coupling effect between the two reactor modules. An engineering simulator of the HTR-PM plant was developed by embedding the THERMIX/BLAST code into the vPower simulation platform. Two sets of nuclear steam supply systems of HTR-PM, including two reactors, two steam generators, two helium blowers, and the helium flow ducts, were simulated by two THERMIX/BLAST code modules, respectively. The entire secondary loop system was simulated using intrinsic models of the vPower simulation platform. The vPower platform connects and synchronizes the two THERMIX/BLAST modules, as well as the simulation module for the secondary loop system. The engineering simulator was applied to simulate the behavior of HTR-PM under steady-state operation, startup and shutdown processes, and accident conditions. The coupling effect during the condition conversion process and the thermal characteristics under accident conditions of HTR-PM were analyzed by the engineering simulator.