Three Intelligent support subsystems have been developed for the module-based simulation system to reduce the user task in plant simulation practice. The one is involved in simulation execution support system SESS-1 for the interconnection task of the input-output variables of the selected modules necessary for simulation program generation. The other two subsystems involved in SESS-2 are to execute the tasks of program diagnosis and input data setup for the generated program by SESS-1. By the introduction of these subsystems, the user task is shown to be alleviated from the results of some example practice for simple simulations of LMFBR.