Abstract: The Adaptive Integral Method (AIM) in conjunction with the Asymptotic Waveform Evaluation (AWE) technique is presented for fast Radar Cross Section (RCS) calculation of arbitrarily shaped perfect electric conductor targets over a broad frequency band. The application of AWE enables fast frequency sweep analysis. The AIM is employed to reduce the matrix storage and to accelerate the matrix-vector multiplications in the solutions of the Taylor coefficients, the computational rate is improved and the memory requirement is reduced. Combining with Automatic Differentiation (AD) technique, the high order frequency derivatives of Greens function required in the hybrid method are calculated. The numerical results presented in this paper are compared with the results obtained by the conventional AIM point-by-point calculations. The proposed hybrid technique can greatly reduce the computation time without loss of accuracy.