The aim of this study was to predict the harvest date and yield of Brassica chinensis L. in plastic tunnels covered with insect-proof screens. A leaf area prediction model for Brassica chinensis L. was developed based on the relationship between leaf area per plant and the product of thermal effectiveness and photosythetically active radiation(TEP). Then a harvest date and yield prediction model was developed by integrating the conventional photosynthesis and dry matter production model and the leaf area model mentioned before. Experimental data of different varieties and sowing dates were used to validate the model. The results show that the determination coefficient (R2) and the relative estimation error (RE) between the predicted and the measured number of unfolding leaves, individual leaf length, leaf area index harvest date and yield based on the 1︰1 line were 0.93, 0.95, 0.97, 0.91, 0.97 and 10.9%, 8.7%, 11.4%, 3.4%、12.5%, respectively. The model developed in this study can give satisfactory predictions of harvest date and yield of Brassica chinensis L. in plastic tunnels covered with insect-proof screens and has strong practicality. Model parameters can be obtained easily.