The heat transfer performances of a sunflower radiator with triangular groove extended surfaces for high-power LEDs are numerically simulated and analyzed. The temperature distribution in the direction of fin length is experimentally tested. Under the condition that the natural convection and radiation model is considered, the effects of apex angle α, groove width s and groove depth d on the maximum temperature rise ΔTmax at the top of fins, average convective heat transfer coefficient h and convective thermal resistance R are investigated. The results show that the existence of triangular grooves with apex angles of 90°-120° and inclining to fin root increases the heat dissipation area and also improves the fluid-flow distribution, and thus the heat transfer performances of sunflower radiator are significantly enhanced. Compared with that of groove width s, the influence of groove depth d on the average convective heat transfer coefficient h is more remarkable. A small or large groove depth deteriorates the heat transfer performance due to the significantly decreased average convective heat transfer coefficient h.