Abstract: A greenhouse microclimate simulation model was developed based on the principle of greenhouse energy and mass (moisture) balances. Experiments were carried out in a Dutch Venlo-type greenhouse in Shanghai during three seasons to collect microclimate and crop data to validate the model. The simulated greenhouse air temperature, humidity and canopy transpiration rate agreed well with the measured data. The correlation determination coefficient (R²) and standard error (SE) between the simulated and measured greenhouse air temperatures, humidities and crop transpiration rates, during the three experimental periods, were 0.89, 0.75, 0.52; 1.1℃, 4.4%, 0.040 gm^-2·s^-1 (August 2001); 0.84, 0.59, 0.73; 1.6℃, 6.0%, 0.012 gm^-2·s^-1 (January 27 to February 5, 2002); 0.80, 0.84, 0.77; 1.5℃, 4.4%, 0.018 gm^-2·s^-1 (June 24 to July 12, 2002), respectively. Based on the results obtained in this study, it is concluded that this model can give satisfactory predictions of greenhouse microclimate under both summer and winter conditions in subtropical China.