The invention provides a voltage optimization control method of an off-grid energy storage converter based on compound control. The optimization control method comprises the steps of summing outputs of repetitive control and PID (Proportion Integration Differentiation) control as a control signal of the energy storage converter, allowing the PID control to adjust a deviation of an effective value of voltage, obtaining PID control quantity, allowing the repetitive control to adjust a deviation of actual output voltage and analog sinusoidal voltage of the energy storage converter, and obtaining repetitive control quantity. The method solves the problem of poor power quality of a power supply system caused by non-linear load connection, and improves the power quality of the power supply system during off-grid operation of the energy storage converter.