Abstract: Matter production and allocation laws inside tomato plant and the organs' dynamic growth rules were discussed to individual plant and organ level.In the model,matter production is computed with the transpiration of the leaves at each cycle.Biomass is allocated to organs,such as inter-node, petiole,blade,and fruit according to their sink strength and expansion laws.The geometric size of organs,as a function of their volume,is derived step by step.The parameters involved in the model are estimated according to the experimental data.By the comparison and analysis among those parameters,certain rules are attained on how and what degree they affect the growth of different organs.Furthermore,the residual analysis was made to test the model outputs.The results verify that this model is acceptable and valid.