The invention discloses a gate water purifying device for a water conservancy project. A small water purifying device is arranged on a water conservation gate so that workers working for the water conservancy project, the outdoor people and animals can drink the purified water conforming to the drinking standard at any time. Each component in the small water purifying device arranged on the water conservation gate is specifically limited, so that the water purifying efficiency under the miniaturization condition is high, and the self production and self use without adding the energy are realized.