Abstract: The inverter of sine pulse width modulation (SPWM) has become the main form of power supply. In order to decrease the harmonics of the SPWM voltage wave and to improve the quality of voltage wave, an improved equiarea algorithm to realize SPWM wave is proposed. In the improved equiarea algorithm the geometry center of sampling period is regarded as the rectangular pulse center of SPWM wave. The harmonics analyses of the algorithm have been done. Finally, the realization of the algorithm based on digital signal processor is given. The analyses results show that the harmonics of this algorithm is decreased obviously and the quality of wave is improved obviously. This algorithm can be used in real time operation to realize sine pulse width modulation.