Module-based Simulation (MSS) has been developed to realize a new software enviroment enabling versatile dynamic simulation of a complex nuclear power plant system flexibly. Described in the paper are (i) fundamental methods utilized in MSS and its software systemization, (ii) development of human interface system to help users in generating integrated simulation programs automatically, and (iii) development of an automatical semantic diagnosis and consultation to automatic input data setup for the MSS-generated programs.