Abstract: The product-of-exponential(POE) formula is introduced into the kinematic parameter identification based on joint trajectories for serial mechanism.Each joint trajectory is measured by CMM (coordinate measurement machine).Then, equations describing each joint trajectory can be obtained by processing the measurement data.According to the definition of the revolute joint and the prismatic joint in POE formula's convention,the actual twists and actual pulse-count equivalents of joint variables can be obtained directly from these equations without the complicated procedures of the link coordinate frames' construction and these coordinate transformation matrixes' reconstruction.The method is implemented to identify the kinematic parameters of the digital brain stereotactic apparatus.The experimental result shows that the method is effective and can be applied to the kinematic calibration of the general serial mechanism.