Although there is a rich history of studies of transpiration, a full description of the mechanisms that control this process still eludes us. This lack is related to the fact that control of this process is distributed over a large range of scales from atmospheric turbulence to the regulation of ion transporter in the membranes of cells. The aim of this study was to determine the actual relationship between muskmelon transpiration and multiple environmental and physiological factors under greenhouse condition. Pot experiments were conducted in a plastic greenhouse and physiological and ecological parameters were periodically measured as well as vegetative development. It is possible to draw some firm conclusions: (1) The diurnal course of muskmelon transpiration appeared as double-peak curve, with the peaks respectively appearing at 12:00 and 16:00; The double-peak curve showed gentle change tendency under water stress condition and acute fluctuation under sufficient water condition.(2)The physiological water requirement coefficients (K, ratio of crop transpiration to atmospheric evaporation) was characteristic index of internal biological control of transpiration, variation of K during whole growth period appeared as a quadratic function; There was a strong relationship between K and leaf area index (LAI), effective accumulated temperature (TU) with high coefficients of determination(R²) of 0.941 and 0.909, respectively; The relationship between K and the two variables were explained with a linear function(K=0.439LAI+0.093) and exponential function(K=-5×10TU²+0.006TU - 0.014).(3)The accumulative transpiration of muskmelon during growth period presented "S" dynamic course feasible for the logistic function to simulate with the independent variable of days(t) after transplanting[ET=70.188/(1+63.553e^-0.106t), R²=0.997].(4)Significant correlation was found between muskmelon daily transpiration and leaf area index (LAI)、daily average temperature (T)、daily average relative humidity (RH)、daily solar radiation accumulation (PAR)、relative soil water content (W); LAI was the decision variable since it made greatest comprehensive effect on transpiration; W was the limiting variable since it made indirect influence on transpiration through other factors such as LAI ;The decision coefficient of surplus factors was 22.13%, indicating that some other factors making significantly impact on transpiration had not been taken into account.(5)The response of muskmelon transpiration to meteorological environmental factors was determined by soil moisture content: the correlation coefficient between daily transpiration and meteorological environmental factors increased with the soil moisture content and reached the peak with the relative soil water content of 70%-80%, then decreased gradually.(5)Crop water stress index(CWSI) quantified the effect of soil water content made on transpiration, decoupling the interference function of meteorological environment; CWSI was significantly related with soil relative effective moisture content (A_w) and a empirical model was constructed (CWSI=-1.203 A_w+0.874,R²=0.809).Plant transpiration was a complicated biological and physical process affected by multiple factors, meanwhile, there was a interaction effect between influencing factors, so the crop transpiration should not be analyzed in isolation. It seems that crop transpiration under greenhouse condition was most closely correlated with the minimum limiting factor, this conclusion was in accord with the law of minimum limiting factor. Further research was necessary to improve mechanistic understanding of transpiration process from crop canopy level to leaf stomata level.