Traditional asymptotic waveform evaluation (AWE) with Moment of Method (MoM) for frequency response fast calculations is analyzed deeply.And an important conclusion is drawn:ill-conditioned coefficient matrix of Pade approximation may be resulted from traditional AWE.Well-conditioned asymptotic waveform evaluation is thus introduced.And an implementation of WCAWE is presented for obtaining the frequency response of the Radar Cross Section (RCS) of arbitrarily shaped three dimensional perfect electric conductor (PEC) bodies.Examples given demonstrate that the numerical computation efficiency is improved drastically using WCAWE.