To solve the problem of large harmonics of output voltage and current of three-phase inverters with unbalanced and non-linear loads, an optimal sliding mode preview repetitive control strategy is proposed to achieve fast response to abnormal conditions such as unbalanced loads and non-linear loads and high precision tracking of reference voltage. Firstly, a preview controller is introduced in the feed-forward compensation link, and an extended state error system including target signal and feedback from lagging link is designed by using difference operator, which converts the control problem of the inverter into the regulation problem of linear discrete system. Furthermore, by using Lyapunov method, linear matrix inequality and design method of optimal controller, an optimal sliding mode preview repetitive controller including sliding mode control, state feedback, repetitive control and preview compensation is obtained. The experimental results show that the distortion rate of voltage waveform decreases from 3. 12% to 0. 78% and the response time decreases from 10 ms to 5 ms when the optimal sliding mode preview repetitive control with linear load. The distortion rate of voltage waveform with non-linear load is reduced from 6. 72% to 0. 92%, which verifies the effectiveness of the proposed method.