The radar receiver signal spectrum is complex and variable, and there exists the phenomenon of spectral aliasing. In order to solve the problem of aliasing and distortion of radar receiver signal spectrum for non-integer period sampling, a signal spectrum reconstruction algorithm is proposed. The sparse signal processing technology is used to reconstruct the target scene, and the low-pass filter is used to process the non-integer periodic sampled signal data to reduce the noise component of interference spectrum analysis and reconstruction. The pseudo-random demodulation single branch AIC is introduced to demodulate the signal using pseudo-random sequence, and the filtered signal is sampled through the ADC sampling rate. Reconstruct the radar receiver signal. Fourier transform is used to carry out spectrum analysis of continuous time signals, and through spectrum aliasing correction, the spectrum aliasing phenomenon between different signal sources can be distinguished and corrected effectively, the accuracy of signal analysis can be improved, and the original spectrum reconstruction can be realized. The test results show that the performance of the proposed algorithm is obviously improved. Under the condition of non-integer periodic sampling, the spectral information of the original signal can be recovered well, and the signal-to-noise ratio can reach more than 40 dB.