IDEF(Integrated Definition) method, a standard methodology of CALS process modelling, was applied to the weapon system R&D process to provide information modelling by analysing about goal, input, output and constraints in the R&D process. The information to be managed in R&D institutes was identified by using SmartER which is the automation program of IDEF1/1X and obtained information modelling for TO-BE model. The work process of weapon system R&D consists of the concept study phase, the exploration development phase, the system development phase, the prototype manufacturing phase, and the report writing of R&D results phase. The information modelling of weapon system R&D is the R&D work process with information sharing by means of IWSDB Since IDEF is suitable for large scale system development like weapon system R&D, further studies on IDEF would be required to achieve the goal of defense CALS.