Cucumber is one of the major vegetables in greenhouse production. Putting maximize the greenhouse input/output as control objective. So it could create favorable microclimate parameters and conditions to fit crop growth and development. The influence of parameters of microclimate (temperature, relative humidity, light intensity) upon the greenhouse input/output and optimum parameters of microclimate system were studied in this paper. The experiment results show that the most important factor affecting greenhouse input/output is temperature and the important order of factors is temperature, relative humidity, and light intensity. The optimized combination of factors is temperature 31℃, relative humidity 85% and light intensity 16klx.