Modeling the deformation of 3D plant is a challenge in computer graphics. This paper presents a simulation method for physically simulating interactive deformation of 3D plant models. This method creates a tetrahedral mesh from the initial triangular plant model, the tetrahedral mesh is then used for dynamic response calculation of collision or interaction, the original triangular mesh is deformed along with the tetrahedral mesh. A capsule-based method and a spatial hashing based method are used for efficient and accurate collision detection. Smooth deformation effects and real-time simulation on 3D plant models demonstrate the effectiveness of our method. The main contribution of this paper is the proposed method can handle the geometric complexity of various plants by a simple model.