Abstract: In this paper,interval generalized Ball curves of Wang-Said type(WSGB) is proposed,it can serve as an effective tool for error control and product testing,three methods are investigated for degree reduction of WSGB,namely,perturbation,best uniform approximation method and constrained best uniform approximation method obtained by Chebyshev polynomial.The explicit representations of the corresponding errors are given,and the advantages and disadvantages of these methods are discussed by some numerical examples.