Abstract: This paper discusses the effects of sampling rate on LFM pulse compression when LFM I/Q Quadrature signals are sampled. The theoretical analysis has proved that in the condition of under-sampling, because the paired echoes will be appeared, the system's multi-object resolution will be affected. In the other hand, after pulse compression processing, the output signal's main lobe will be extended and its amplitude or phase will be modulated, and the range resolution will descend too. Finally, some simulation results have been displayed.