The utility model discloses an active emergent injected water system of non - for nuclear main pump bearing seal, include: the main pump, hydrocyclone, hydrocyclone is connected the circulation circuit that formation can switch on through a plurality of valves and main pump, and high -pressure cooler, the 2nd circulation circuit that formation can switch on is connected through a plurality of valves to hydrocyclone, high -pressure cooler and main pump, wherein: the bearing seal injected water is imported in the bearing seal chamber of hydrocyclone postinjection main pump by bearing seal injected water pipeline to the main pump operation, perhaps by the bearing seal injected water of emergent bearing seal injected water pipeline input in the bearing seal chamber of the cooling postinjection main pump of hydrocyclone and high -pressure cooler. Implement the utility model discloses an active emergent injected water system of non - for nuclear main pump bearing seal can form the complementation with currentization of nuclear main pump appearance control system, guarantees the reliability of main pump bearing seal water injection under the multiple condition, adopting the active mode of non -, further reducing the bearing seal damage, safety ring protects, be convenient for device structure and maintenance.