In order to research the factors that affect the current uniformity of Flip-chip LEDs, the three-dimensional model of LED chip is established by the finite-element analysis software COMSOL4.0. The influences of chip size, electrode structure and current injection bump on the electrical property of the LED are investigated. The simulation results show that the non-uniform current distribution of LED chip changes exponentially with the increase of the chip size. Interdigitated electrode structure can reduce the lateral resistance effectively by shorting the channel that current flows through. The reasonable design of the bump on the block electrode can also make current even by reducing the lateral resistance.