The impact of the refractive index and thickness of substrate on the light extraction efficiency of flipchip LED is analyzed through simulation analysis. And a new diamondshaped structure is proposed. The results show that the light extraction efficiency is improved to a good purpose in the diamondshaped LED, resulting in an increase in the light extraction efficiency by 1.51,2.03 or 3.65 times when the substrate is Si, Sapphire or SiC espectively.