Abstract: The air circulation and microclimate distribution in a forced ventilation greenhouse with pad and fan cooling system was analyzed by means of computational fluid dynamics (CFD) based on the finite element method. The simulation concerned the distribution of temperature, airflow, humidity in the latitudinal cross-section in the greenhouse. Two cases in two operation conditions (1. only pad operation, 2. pad and fan operation) were investigated: in the first case there was no crop inside the greenhouse, while in the second greenhouse, the crop was simulated as porous material and was governed by the Darcy-Forcheimier equation in the model. The model simulations were validated with respect to temperature, airflow speed and relative humidity field measurement inside the experimental greenhouse. The simulation errors were 0.10% to 2.63%, 0.81% to 18.54% and 2.0%-12.64% for air velocity, air temperature and humidity respectively at the observation points.