This paper describes several main monomial cooling methods of greenhouse in summer, including natural ventilation, mechanical ventilation, wet curtain cooling, external sun-shading etc., as well as analyzes the change law of the environment on temperature and humidity in greenhouse. The result shows that the four cooling methods stated above make the temperature gradients between internal and external respectively 1.1℃, 0.4℃, -2.6℃ and -1.2℃,so it is obvious that the cooling effect of wet curtain cooling is the optimum; and the internal and external humidity difference is respectively: -13%, 6%, 8% and 1%.