A tree geometric modeling method based on the theory of L-systems was proposed in this paper, which was faithful to the plant morphology and the physiological ecology of tree growth process.Under its guidance and restraints, the dual purposes of “to restore status truly” and “to simulate processes scientifically” were reached. A method to compound L-system rule from organ scale to the whole tree scale was proposed, which could make the plant morphological and growth rule be reused easily. The function and architecture of LSTree software was designed. It was developed with VC++, OpenGL Graphics standard, VRML (virtual reality modeling language) and Microsoft’s MSXML application programming interface. The system has many functions such as input and output of tree model, three-dimensional display of trees, simulation of the tree growth process, etc. It provides a better human-computer interaction and a flexible, scientific way to manage and organize the model. The system is useful in many fields such as education, propaganda and scientific research on botany and ecology, precision agriculture.