The invention discloses a method for reusing liquid waste in a pressurized water reactor nuclear power station. The method comprises the following steps of: processing the liquid waste by use of a liquid waste processing system, and monitoring the quality of the processed liquid waste by a liquid waste monitoring tank; sending the qualified liquid waste to a spent fuel pool as a water supply of the spent fuel pool. The invention also discloses a system for reusing the liquid waste in the pressurized water reactor nuclear power station, which comprises a liquid waste processing system, a liquid waste monitoring tank connected with the liquid waste processing system and used for monitoring the quality of the processed liquid waste, and a spent fuel pool connected with the liquid waste monitoring tank to contain the qualified liquid waste as a water supply. Compared with the prior art, the processed liquid waste is used as evaporative supply water of the spent fuel pool in the invention, the water supply volume of the spent fuel pool is essentially flat to the liquid waste processing volume, thus, the closed-loop circulation can be realized, and the liquid waste outlet problem under the strict plant address discharge condition can be solved.