B-spline method plays an important role in data interpolating, fitting and smoothing. Through analyzing the computed path of the de Boor-Cox algorithm, a new method for calculating B-spline function is given based on the vector extending operation. The proposed method has a parallel computing architecture and is suitable to realize by computers. Compared with the de Boor-Cox algorithm, the proposed method can improve computing efficiency by (2k+1) times in the task of calculating all nonzero values of k-degree B-spine functions. As an application in B-spline curve fitting, it shows that the proposed algorithm can reduce the computing efforts obviously.