It is an important issue to evaluate the effectiveness of chemical warfare through modeling and simulation(M&S) technology. In this paper, we propose the M&S methodology and environment for the chemical warfare for effectiveness analysis. In detail, for modeling perspective, we propose three fundamental component models according to their behaviors, which are a chemical weapon, a detecting device system, and an engaging unit system. Among proposed models, the chemical weapon and the detecting device system models are represented by engineering-level system models, whereas the engaging unit system model are described as an engagement-level system model. For simulation perspective, we apply a hybrid simulation environment using High Level Architecture (HLA) to interoperate with the proposed engineering and engagement-level models. The proposed M&S methodology and environment enables to evaluate the effectiveness of the chemical warfare system considering the doctrines, the performance of device or weapon, and weather factors. To verify the efficiency of the proposed methodology and environment, we experimented three categorized case studies, which are related with those considering factors.