The Sinusoidal Pulse Width Modulation (SPWM) wave is very important for the design of frequency and voltage adjustable DC to AC inverters. Currently, SPWM waves are usually generated through the pulse width modulation (PWM) pins of a singer-chip microcomputer or digital signal processor (DSP). In order to achieve desired SPWM waves and know them better, it is essential to analyze their harmonic components. In this paper, we introduce a new approach to the harmonic analysis of SPWM waves based on Discrete Fourier Series (DFS) and the area equivalent principle. The developed method is convenient and the results of simulation and experiments are more accurate compared to conventional methods. The advantages of our approach are confirmed by the simulation and experimental results.