The invention discloses a wafer back surface pollution prevention device which is applied to semiconductor uniwafer cleaning equipment. The wafer back surface pollution prevention device comprises a nitrogen cover which is concentrically arranged at the upper surface of a rotating clamping disc. An air ejection mechanism is convexly arranged at the middle part of the upper surface of the nitrogen cover. Multiple air outlets are evenly arranged around the side surface of the air ejection mechanism. The air outlets are arranged in a manner of facing the edge direction of the back surface of a wafer arranged on the air outlets in a radiation shape at a certain upward tilting angle so that taking and placing of the wafer of a manipulator are not influenced, and a circle of inverted umbrella-shaped air protective layer intersected with the edge of the back surface of the wafer is enabled to be formed by air ejected out of the air outlets. Therefore, the whole back surface of the wafer is ensured to be protected by air, the back splashed cleaning fluid can be effectively blocked and thus secondary pollution to the back surface of the wafer can be avoided.