In this study, CNG (Compressed natural gas) composite vessel is analyzed by using a coupled model with liner and composite layer. For the coupled model, the method by using theoretical analysis and FEA is suggested. The elastic solution for laminated tube is used in the theoretical analysis of composite vessel, and FEA is performed by using the model of CNG composite vessel with actual conditions. On the basis of these results, optimal thickness and winding angle of the composite layer are determined by considering material property and thickness of the liner. The results of theoretical analysis and FEA are compared with the previous study results to verify the proposed analysis method.