The invention relates to a power supply system of a photovoltaic inverter suitable for the lower voltage ride-through requirement and a power supply method thereof. The power supply system comprises an alternating current (AC) power supply and a direct current (DC) power supply, wherein the AC power supply is connected with the grid connected side and connected with a control system and a contactor coil respectively through a bridge rectifier module (DB1) and a bridge rectifier module (DB2); and the DC power supply is connected with the photovoltaic array DC side and connected with the contactor coil and the control system through a DC/DC convector. According to the power supply system and the method thereof, the AC/DC redundancy power supply mode is adopted, the control system and the contactor coil are powered respectively, and the problem of falling of the contactor coil due to power loss from a grid when a low voltage ride-through failure occurs in the grid in the prior art is solved.