A power conversion system with ripple injection includes an AC-DC conversion unit, a voltage regulation unit, at least one DC-DC conversion unit, at least one load, and a first control unit. The voltage regulation unit provides a DC link and receives one portion of an input power as an energy storage power. Each DC-DC conversion unit receives the other portion of the input power as an output power. The at least one load correspondingly receives the output power for being supplied power. The first control unit is coupled to the DC link, the at least one DC-DC conversion unit, and the at least one load. The first control unit controls the at least one DC-DC conversion unit to adjust a magnitude of a ripple of the output power to perform a ripple injection operation according to a magnitude of a ripple of the input power.