In this study, we investigate the impact on the aerodynamic performance and the flow field of civil aircraft with multiple winglets through numerical fluid analysis. The concept of multi-winglets, inspired by the primary feathers of birds, aims to emulate their function in reducing induced drag by dispersing wingtip vortices. Previous research applied multi winglets on an unmanned aerial vehicle and found that they had a similar effect on their functions in birds. An additional achievement was an increase in lift by narrowing the gap between winglets. However, there have been few studies of applying three or more winglets to civil aircraft, and the physical effects on the flow field resulting from the installation of multi winglets remain unexplored. Therefore, we installed three winglets on the NASA Common Research Model and conducted numerical analysis under takeoff/landing and cruise conditions. For the Multi winglet model, the conventional single blended winglet was divided into three sections spanwise, creating a configuration with different cant angles for each winglet. Additionally, we calculated for the single blended winglet before division. A comparison was made between the influences on the multi-winglet's aerodynamic performance and flow field.