Abstract: Air temperature in the uncooled greenhouse is much higher than 40℃ in summer in China,and severely affects plant growth.With fan and pad evaporative cooling system, the temperature inside greenhouse can be maintained below 30℃ in very high ambient temperature and radiation iuteusity.A mathematical model is developed to predict the thermal behavior of these greenhouses. And a compute program is provided which includes the evaporative pad efficiency, the average temperature and the relative humidity, thed istributions aud the variation of airtemperature and relative humidity from air inlet to exhaust. This model can also be used for ventilation analysis of uncooled air. Confirmed by experimental data the model seems to predict with reasonable accuracy. From the analysis some data ma be useful for greenhouse desin and operation.