Current robot calibration schemes usually employ calibration models with constant error parameters. Consequently, they are inevitably subject to a certain degree of locality, i.e., the calibrated error parameters (CEPs) will produce the desired accuracy only in certain regions of the robot workspace. This is mainly because of incomplete modeling of errors, resulting in imprecision, and because only a limited amount of measured data are available for identifying CEPs. To deal with the locality phenomenon, CEPs that vary in different regions of the robot workspace may be more appropriate. Hence, we propose a variable D-H (Denavit and Hartenberg ) parameter model to formulate variations of CEPs. Simulations and experiments that verify the effectiveness of the proposed calibration system are described.