The traditional three-level space vector pulse width modulation（SVPWM）algorithm needs a great deal of calculation. To achieve the simple implementation of the three-level SVPWM algorithm, a simple algorithm, based on unified voltage modulation, is proposed in this paper. Firstly, a simplified two level SVPWM algorithm is introduced in detail. Then, the method of converting the three level to the two level is discussed. Finally, a custom model is built in PSCAD/EMTDC to implement the simplified three level SVPWM algorithm, and it is applied to the simulation control of three-level photovoltaic inverter. The simulation and experimental results verify the effectiveness of the proposed algorithm.