This paper introduces an effort to precisely describe attitude motion under full orbit perturbations. To define the attitude of an Earth-orbiting spacecraft, this study introduces a reference frame being affected by orbit perturbations. Unlike the commonly adopted reference frame, the reference frame introduced here is fully perturbed, so that it rotates about not only the pitch axis, but also the yaw axis. To incorporate the mutual coupling effect between attitude motion and orbit motion, the method introduced considers the spacecraft as consisting of multiple facets and carefully models orbit perturbation-induced torque that varies the attitude. This paper focuses on the attitude dynamics of a small satellite with relatively low moments of inertia under full orbit perturbations, and provides some interesting results and the outcome from the method introduced.