Abstract: For the sake of improving decision-making performance of agricultural expert system and dynamically describing the results of reference, an expert system for greenhouse tomato planting based on virtual plant growth model was built. The architecture and the functional modules of system were introduced at first, and then some key techniques, such as software tool for developing expert system, knowledge representation, construction of knowledge library, and building the virtual tomato growth model were presented in detail. The developed expert system for tomato planting management in greenhouse synthetically utilized reasoning, prediction, visualization, and interpretation, etc, to design planting strategies, visually simulate and predict the process of tomato growth. The integration of morphogenetic model, knowledge model, and model of accumulated temperature was primarily realized in the developed expert system, thus made it meet the practical demand of tomato planting better. Experiments showed that the developed expert system possessed a better future of applications.