Abstract: In order to clearly understand the mechanism of heat and mass exchanges between the interior and exterior air of a plastic tunnel greenhouse, the Gembloux Greenhouse Dynamic Model (GGDM ) used for the large glasshouses was applied to small plastic tunnel in which the conductive, convective, solar and thermal radiative as well as latent heat exchanges among 3 soil layers, vegetation, interior air, cover and thermal screen were taken into account. The comparative analysis between simulation and measurement was carried out under the different climate conditions. The results of validation show that the high degree of accuracy and reliability of the model is reached.