The invention discloses a water conveying valve top water stop cavitation preventing method and structural arrangement. A water conveying valve top water stop head cylindrical cavity is utilized as a ventilation transverse pipe, a system ventilation pipeline is formed by arranging a ventilation main steel pipe, a check valve, a ventilation main hose and a ventilation branch pipe, automatic ventilation pipeline ventilation is achieved through the negative pressure generated behind the narrowest fracture surface through narrow slit high-speed jet flow at the beginning of the opening of a water conveying valve, the top water stop cavitation of the water conveying valve is restrained, impact vibration generated at the beginning of the water conveying valve is eliminated, and safe and stable running of the water conveying valve is guaranteed. According to the water conveying valve top water stop cavitation preventing method and the structural arrangement, the structure is simple, operation is easy, and the cavitation preventing effect is obvious.