For the characteristic of off-grid three-phase inverter with unbalanced load in photovoltaic power system. The paper analyzed the off-grid three-phase inverter circuit topology structure and its corresponding control method in detail. Analyzed three-phase three-leg inverter circuit, introduced instantaneous capacitor-current feedback control, at the same time used split-phase control for three-phase output voltage by LCL-filtered. The output voltage of each phase compared with reference voltage used PI operation, and then compared with capacitor current produced K as SPWM pulse to control switch component, to realize the three-phase inverter output voltage balanced. With Matlab/Simulink simulation model presented. The analysis of simulation displayed that the control method applied in this paper, with serious imbalanced three-phase load, output voltage of three-phase’s imbalance degree was small, also with stronger nonlinear load capacity. Accordingly, the balanced output voltage is guaranteed under any unbalanced loads.