Based on the finger dynamic model, velocity observer was constructed for adaptive curve fitting. The adaptive control with observer made up the limit from short of velocity sensors and complemented the uncertain factors from underactuated components. In compare with PID control or computed torque, the observer reduced fitting errors and achieved ideal dynamic control results. On the other hand the force based impedance control strategy had been constructed based on dynamic model. The velocity observer had been used in impedance control. The strategy could not only realize accurate force tracking, but achieve finger’s dynamic control by the combination of curve fitting and force tracking.