A summary of quaternion in the kinematics of rigid body dynamics is presented. Quaternion is a four-parameter system for specifying the orientation of a rigid body. Four parameters of quaternion are updated by integrating linear differential equations whose coefficients are the angular velocity of the body. After describing the coordinate systems and vectors, quatemion is introduced. Then, using a comparison with the Euler angles, typical presentation of body orientation and the relationships betweenquatermion and angular velocity are discussed. Finally, a computer simulation algorithm is deriverd to solve rigid body dynamics using quatermion.