The invention discloses a water surface projection advertising device which comprises an emission source, a refraction and projection device and a water curtain. The emission source comprises a condensing plate, an LED high-frequency flashing strip, an advertisement storage database and an intelligent processing circuit board. The intelligent processing circuit board reads contents in the advertisement storage database and drives the LED high-frequency flashing strip to perform high-frequency flashing according to the contents in the advertisement storage database, and the contents are projected to a polygonal lens through the condensing plate and finally reflected to the water curtain through the polygonal lens. The refraction and projection device comprises the polygonal lens in connection with a high-speed motor, the water curtain comprises a water reservoir and a water tank, and the water tank is connected with a pumping motor. By high-speed rotation of the polygonal lens, dynamicadvertising pictures are refracted to the water curtain, advertising expense is saved for users while a great quantity of advertising paper sheets are saved, and resource saving and environmental protection are realized; due to recyclability of water in the water curtain, water resources are saved.