IFFT(inverse fast Fourier transform) technique is usually used in high resolution radar imaging with stepped frequency signal. However, due to the high side-lobes introduced by IFFT, the weak scatters or small targets may be covered by the range side-lobes of the strong scatters, which limit its application in the strong clutter environment. In order to suppress the high range sidelobes, APC (adaptive pulse compression) algorithm based on MMSE (minimum mean square error) has been proposed in recent years. Based on the model of APC algorithm, the APC algorithm of stepped frequency signal for stationary and moving target was detruded. Simulation results show that the APC algorithm has a better side-lobe suppression effect when compared with the IFFT method and the windowed processing, and it can detect weak scatter or small target in the neighborhood of the strong one better.