On the basis of the method of action-angle variables the conditions of closed orbits under the action of general power-type gravitation potential are discussed on this paper. By method it is unnecessary to assume that the initial orbit is near to a circular orbit. Form of gravitation potential can be extented to the inverse proportional force field and other power force field. The discrimination formula of the closed orbits is given. Finally，if the central force contains an r^-2 term and an r^-3 term，as provided by relativistic corrections，then the orbit is closed and is in the form of a precessing ellipse. Finally the precessing angular velocity of the ellipse is calculated.