ZnO columnar and cone-shaped micro-nano structures were grown on the surface of GaN-based LEDs by using the finite difference time domain method (FDTD). The Rsoft simulation software was used to analyze the influence of the geometric parameters of the two structures, such as the arrangement period P, height H, bottom diameter D, etc., on the light extraction efficiency of GaN-based LEDs. The results show that both structures can improve the light extraction efficiency of the device. The columnar structure performs the best when H=0.25μm, P=1.5μm and D=0.9μm, and its light extraction efficiency is 5.6 times that of flat panel LEDs without any structure. The cone-shaped structure performs the best when H=0.6μm, P=1.4μm, and D=1.4μm, and its light extraction efficiency is 5.3 times that of flat panel LEDs without any structure.