InGaN flip-chip light-emitting diodes on bulk GaN substrate (FS-FCLEDs) with hemisphere-cones-hybrid surface were fabricated using both dry etching with CsCl nanoislands as mask and chemical wet etching. Compared with the corresponding flat LEDs, the light output power of FS-FCLEDs with combined nanostructures shows an enhancement factor of 1.9 at 350mA injection current. Finite-difference time-domain (FDTD) simulation results show that such enhancement of the output power is mainly attributed to the reduction of the total internal reflection and increase of the light scattering probability in the hemisphere-cones-hybrid surface, which is due to a combination effect of light diffraction at the nanocones edges, and light interference within the hemisphere and nanocones.