The invention discloses a reactor core water injection evaluation method for a nuclear power plant equipped with a reactor core catcher. The method comprises the following steps that S1, a reactor core melting process in a pressure container is simplified to three stages; and S2, in combination with a specific reactor core melting process, the water injection evaluation method comprises the following sub-steps of S21, monitoring a process of relocating reactor core molten debris in the pressure container, judging a state of reactor core melting according to instrument monitoring data, and performing analysis in combination with a specific reactor core state to determine a reactor core water injection strategy; S22, monitoring a cooling effect of reactor core water injection, and further adjusting the reactor core water injection strategy; S23, when melt-through of a lower seal head of the pressure container is monitored, stopping water injection; and S24, monitoring melt-through scale and duration of the pressure container, and performing reactor core water injection according to actual position and state of the reactor core molten debris. The method has the beneficial effects that different water injection strategies are given in different accident stages; the water injection flow is controlled according to the cooling effect, so that steam explosion is avoided; and resources are reasonably utilized.