A liquid cooling system includes a heat conductive member, a liquid tank, and plural conduits connecting the heat conductive member with the liquid tank. The heat conductive member is configured for thermally connecting to a heat-generating electronic component. The liquid tank defines a liquid injection hole therein. A clip assembly is connected to the liquid tank. When pressed against the clip assembly by a user, the liquid tank is fastened by the clip assembly and thus retained in position. When pressed again toward the clip assembly, the liquid tank is released from the clip assembly and ejected in a direction away from the heat-generating electronic component. An electronic device using the liquid cooling system is also provided.