Abstract: To estimate the plant transpiration water consumption of urban greenland accurately and conveniently, the response relationship between sap flow density and environmental factors of Ginkgo biloba was studied in this paper. Based on relative efficiency soil water (REW), photo synthetically active radiation (PAR), deficit vapor pressure(DVP), wind speed (W), the response relationship between sap flow and environmental factors were analyzed. So as to analyze the interaction between each factor and sap flow, and determine the key threshold, discrete statistical analysis was given to groups of the environmental variable factors, which was excluded the influence of other environmental factors. Finally, based upon the response process and empirical formula of sap flow-evaporation-stoma above to environmental factors, the relational model of sap flow and environmental factors was built. The results were as follows: 1) the effects of soil moisture on sap flow were restricted with specific threshold value. When the relative extractable soil water REW was higher than 62%, soil moisture was unlimited to sap flow of G. biloba. While when REW was lower than 62%, soil moisture was a limiting factor for sap flow, and the relationship between sap flow and soil moisture can be described by half value empirical functions. 2) Photo synthetically active radiation(PAR) was the driving factor for sap flow, with the driving effect being stronger when PAR was lower than 0.39 mmol/(m2second), while it reached saturation when PAR was higher than 0.8 mmol/(m2second). The relationship between sap flow and PAR could be described by hyperbolic functions. 3)Deficient vapor pressure爷s function to sap flow was dual, when DVP was lower than 3.2 kPa, it had driving effect and the relationship between them could be described by hyperbolic functions. While DVP was higher than 3.2 kPa, it was restricting functions which can be described by half value empirical functions. 4) Wind was a restricting factor for sap flow, but it worked only when wind speed was 4 m/second. The relationship between sap flow and wind speed could be described by half value empirical functions. 5) The accuracy of sap flow-environmental factors model was tested. The results showed that the determination coefficient R2 of simulation on hourly sap flow density was 0.799 8, and relative deviation was 17%, while the determination coefficient R2 of simulation diurnal sap flow density was 0.895 2, and relative deviation was 10%.