An efficient numerical approach is presented to accelerate the solution of the wideband electromagnetic scattering characteristics using the ultrawideband characteristic basis function method （UCBFM） with the best uniform approximation.The ultrawideband characteristic basis functions （UCBFs） are obtained at the highest frequency point，these UCBFs can be reused for each node of Chebyshev，so the time of calculating the surface electric currents at these nodes can be greatly saved.Then，the electric current distribution can be obtained at any frequency within the given frequency range by using the best uniform approximation，which is used to compute the scattered fields and the wideband radar cross section （RCS）.The accuracy and efficiency are improved significantly compared with the traditional ultrawideband characteristic basis function method （UCBFM）.Numerical results demonstrate that the proposed method is accurate and effective.