Moisture content of moulding sand is very important,but it veries easily by evaporation, so if mixed theoretically the content becomes too low for actual use. So how to retard or how to accelerate the vaporizing speed is very important. In this report the author studied the effects of various factors on the vaporizing speed of moisture in foundry sand at ordinary temperature and at high temperature,and determined how to retard or how to accelerate the vaporizing speed.