Plants 3D structure is quite complex. This paper presents an Open Synthetic Plant Modeling Method. It includes three parts:plants realistic representation model,synthetic modeling method and realistic display method. Branch is the base element of plants realistic representation model and is simulated by cublic parameter surface. The synthetic modeling method is implemented by interactively using several simulation methods in the growth procedure of plant. Bark texture and leaf are added to realistically display the plants 3D structure, Four test examples indicate that this method is feasible in plants 3D modeling.