The dynamics of continental plates has been one of the major subjects in the context of geoscience and the hypothesis on the driving mechanics has been controversial for over a half of this century. Much evidence shows that the plate motion bears a relation to the earth’s rotation in such a way that it is markedly directional, i.e. either vertical or parallel to the rotational axis.Starting from the principles of mechanics, the paper investigates the characteristics of a light body in a rotational frame. followed by addressing the state of a floating body in such a system. It is believed that such model applies utterly to the study of geoplates.One of the basic principles in the theory on plate techtonics states that since plates of different sizes float over the plastic movable sphere. the high fluidity of the matter therein gives rise to the drift of the plates. On account of the rotation, plates are under the effect of a force system.This article Is confined to the discussion of the effects on the plate motion ofthe principal moment acting eastward along the parallel and the dominant vector acting equatorward, the former responsible for the inclination with the head(tail) downward(up-) and the latter leading the center of mass of the plate to translate equatorward,i. e., the plate travels equatorward in a manner of head (tail)downward(up-).