Abstract: In accordance with the lifting travel and the lifting power of low-powered tractor with four wheels, a CAD method for determniing the parameters of implement-hitch linkage and the weight limitation of mounted implement is developed, and a reasonable area of the implement's instantaneous rotating-center is suggested in this paper. The results gained using this method and its program show that (i) the increase of mounted implement's design wieght and its moment of entering the ground is in contradiction with the increase of the angle, which is formed by the inclination of headstock's vertical column when the mounted implement is at the highest position, (ii) combining this method with the optimum objective, we can rapidly find out the best scheme for designing the papameters of implement-hitch linkage and the weight limitation of mounted implement.