A calibration device for a computer-assisted surgical instrument includes a rigid body, stabilization members, and references structurally or mechanically complementary to the stabilization members and disposed on opposite sides of a manipulator of the instrument. Kinematic state of the manipulator is defaulted when the calibration device is connected to the instrument by the stabilization members passing through the rigid body and removably attaching to the references. A calibration method for a computer-assisted surgical instrument implemented by a computer system includes the steps of: prompting a user to connect the calibration device to the instrument； determining if the calibration device is properly connected to the instrument； and generating default kinematic information of the manipulator of the instrument if the calibration device is properly connected to the instrument. The calibration device and method effectively improve accuracy and precision of computer-assisted surgeries.
