The invention discloses an off-grid inverter control method and system. According to the off-grid inverter control method and system, the output of a control loop is changed through adding load current differential feed-forward control and capacitance-voltage differential feed-forward control to the control loop, and then the impedance change of the output load is overlapped so as to enable the controlled quantity output by the control loop to change along with the load change, after the load is changed, the control loop quickly responds to the change to enable the output voltage to be more stable and the electricity use load to be safer.