Abstract: The cooling system based on the water-cooled and air-cooled combination was designed for simplifying the cooling system, reducing the size and lowering the cost. It has the advantages of both water-cooled and air-cooled systems, and can achieve stable green laser output. LD endpumped Nd∶YVO4 and KTP green laser with the simple and compact flat-concave cavity design was obtained. When the crystal absorbs the pumping power of 24.3W, the 532nm laser power is 4.2W and light-optical conversion efficiency is 17.2%. The power change range of about 2.5% and the temperature change range of about 0.1 were observed as the green output power was 3W. The experimental results show that the cooling system can effectively transfer the heat produced by the thermal effect of the crystal, and higher conversion efficiency of green light output can be realized. The technology is favorable to the miniaturization of high-power laser.