Abstract: A large-scale weighing lysimeter was employed to study cucumber transpiration processes in solar greenhouse in Beijing. Based on the cucumber growing processes, the growing season was divided into three stages: flowering-setting, fruiting and later fruiting with stage transpiration 14.06 mm, 102.85 mm, and 30.84 mm, respectively. The cucumber seasonal transpiration was 147.74 mm and the seasonal average transpiration rate was 1.41 mm/d. The most sensitive factor to transpiration rate was net radiation followed by air relative humidity, pan evaporation, leaf area index (LAI), and air temperature in order. Three empirical models were also proposed for estimation of cucumber transpiration rate in solar greenhouse.