Abstract: It is a very important part for crop transpiration in the process of crop growth. For seeking suitable transpiration estimating model of tomato grown in greenhouse, the parameters such as canopy stomatal resistance of tomato and aerodynamic resistance were modified in connection with a microclimate environment in greenhouse based on Penman-Monteith equation, and the estimation model of transpiration for greenhouse-grown tomato was established by considering the meteorological data, leaf area index and canopy height as main parameters. The model was verified by measurement values of sap flow rate from May 2 to 13 in 2009 (at the flowering and fruit development stage) and from June 9 to 20 in 2009 (at the fruit maturation stage), respectively. The result showed that average relative error for the model simulation was 8.48% and 9.20% at two stages, respectively. Therefore, plant transpiration could be estimated using the model. The transpiration model established in this study could provide important reference value to further research on tomato-water relationship in greenhouse.