Major aerospace developers continue to push for new structural composite applications to reduce the environmental impact of greenhouse gas emissions, improve both aircraft performance and costs. In this study, the parts that carry the load in the regions where mechanical joints are applied, require whole processing to tighten and identify stress concentration points. In addition, failure modes caused by bearing and by-pass loads were set as the main design factors. Optimum sizing was performed through the application of factors taken into account in the buckling failure mode and production using the preliminary design analysis model of the composite wing structure. In the area where the fuselage is joined with the fuselage, bearing and bypass load were considered important design factors.