Abstract: In order to forecast the air temperature and relative humidity inside a plastic tunnel with insect-proof nets, a model for simulating the air temperature and humidity inside a plastic greenhouse tunnel covered with insect-proof nets was developed based on the energy and mass balance analysis. Experiments were carried out in a plastic greenhouse tunnel covered with insect-proof nets located in Shanghai City to collect data to validate the model. The model can predict the air temperature and humidity inside the plastic greenhouse tunnel covered with insect-proof nets with such inputs as the outside hourly weather data (global radiation, temperature, relative humidity, wind speed, air pressure), information of greenhouse structure (volume, cover surface area, area of vents, floor area), transmittance of cover material and porosity of the insect-proof net material, and crop information (canopy leaf area index and leaf width). The results showed that the simulated air temperature and relative humidity inside the plastic greenhouse tunnel agreed well with the measured data. The determination coefficient (R2) between the simulation and measured air temperature inside the plastic greenhouse tunnel under sunny, cloudy, and overcast conditions was 0.93, 0.92, and 0.87, respectively, and the root mean squared error (RMSE) was 1.3, 1.4, and 0.9℃, respectively. The R2 between the simulation and measured air relative humidity inside the plastic greenhouse tunnel under sunny, cloudy, and overcast conditions was 0.91, 0.90, and 0.89, respectively, and the RMSE was 4.1%, 4.7%, and 3.2%, SE was 4.8%, 5.6%, and 3.8%, respectively. The model can be used for the optimisation of the greenhouse tunnel structure as well as for the improvement of greenhouse tunnel climate management.