With technological advancements, weapon system development has become increasingly complex and costly. Using modeling and simulation (M&S) technology in the conceptual design stage is effective in reducing the development time and cost of weapons. One way to reduce the complexity and trial-and-error associated with weapon development using M&S technology is to develop combat scenarios to review the functions assigned to new weapons. Although the M&S technology is applicable, it is difficult to analyze how effectively the weapons are functioning, because of the dynamic features inherent in combat scenario modeling, which considers interrelations among different weapon entities. To support review of weapon functions including these characteristics, this study develops a process-based modeling (PBM) method to model the interactions between weapons in the combat scenario. This method includes the following three steps: (1) construct virtual models by converting the weapons and the weapon functions into their corresponding components; (2) generate the combat process from the combat scenario, which is derived from the interrelations among weapons under consideration using reasoning rules; (3) develop a process-based model that describes weapon functions by combining the combat process with virtual models. Then, a PBM system based on this method is implemented. The case study executed on this system shows that it is useful in deriving process-based models from various combat scenarios, analyzing weapon functions using the derived models, and reducing weapon development issues in the conceptual design stage.