Abstract: In some applications, sampling with Nyquist frequency may be hard to implement due to hardware limitation. Based on subsampling, a method which estimates the modulation rate and initial frequency of the ultra-wideband LFM signal is presented in this paper. Based on the cross-spectra ESPRIT algorithm and remainder theorem, the modulation rate and initial frequency of the subsampling ultra-wideband LFM signal are estimated unambiguously and precisely even in low SNR. Simulation confirms the validity of the method.