An approach to the estimation of the motion and structure parameters of brachium and leg based on monocular image sequence is proposed. By using the motion description under the object-centered coordinate system, a non rigid motion model based on the notion of elasticity is developed. The non-rigid motion model and the rigid one are well unified by incorporating the elasticity parameters into the rigid motion model. Based on this model, the motion and structure parameters are estimated using the method of Levenberg-Marquardt. Results show that the metlod is effective and the motion pattern can be reflected to some extent by the elasticity parameters.