One of the most important factors affecting the aerodynamic performance of the aircraft is lift-induced drag caused by wingtip vortices. This study describes the winglet design and analysis for solar-powered unmanned air vehicle (UAV). The motivation of this study is designing elliptical winglet to explore efficient shapes using multiple winglet parameters such as cant angle, sweep angle, taper ratio, toe angle and twist angle. The aim was to investigate the performance of parameters that constitute the winglet and to find the best elliptical winglet design which has the highest L/D ratio according to design parameters by using computational fluid dynamics. The aerodynamic characteristics of lift coefficient (CL), drag coefficient (CD) and lift to drag ratio (L/D) were compared for 39 different winglet models for cruise conditions of UAV. Analyses showed that, elliptical winglet increased L/D ratio on the order of 8.32% compared with the baseline wing.