To model smooth surfaces representing tree branches by using implicit surfaces to improve the diversity of computer generated tree branch surfaces，and to bring realistic description of its local details，a method is proposed to model 3D tree surfaces.This method combines implicit surfaces based on skeletons and convolution surfaces based on line segment primitive with polynomial density distribution.The BlobTree provides several techniques to control the combination of primitives.Better blending is used to remove the blending bulges.It is showed that smooth blends can be obtained without noticeable bulging.PCM (precise contact modeling) is used to model local details on the face of trunk and branch of the tree.The appearance of the generated tree model is improved by using color filling，while the used colors are selected from the real tree branch image according to a probability distribution.Experimental results demonstrate that the proposed method can reconstruct various smooth 3D tree branches with local detail features such as branch bark ridges and tree bulges.