This paper proposes base parameters identification method for hydraulic manipulators. First, the state-space equation of hydraulic manipulators is converted into a linear equation with respect to base parameters which are a set of unknown parameters such as the flow coefficient, the pipeline volume and the pressure loss coefficient. Second, a new parameter identification method is proposed based on the linear equation. Finally, the validity of the proposed method is confirmed via the model validation using an actual manipulator. By the proposed method, not only the manipulator position, but also the pressures of the actual manipulator are close to those of the nonlinear model which is constructed from the identified parameters. Especially, a characteristic response of the actual pressures is also generated by the nonlinear model.