In the electromagnetic radiation information leakage of computer system, video signal can be intercepted and recovered easily. Aiming at the problem of video signal recovery of VGA cable radiation in computer system. The transmission and electromagnetic radiation model of computer analog video signal in VGA transmission channel are established. The imaging rules of analog video signal and the time domain characteristics of analog video signal in each stage during transmission are analyzed. The recovery steps of analog video signal radiated by VGA cable are obtained. Due to the poor quality of the quality of single frame video signal recovered at low sampling rate, according to the image presentation rules of video signal, multiple consecutive recovered images are overlapped, and the recovered image with high quality can be obtained at low sampling rate. Simulation results show that this method can effectively improve the quality of video image restoration, especially at low sampling rate. In order to verify the correctness of the simulation results, the actual intercepted VGA cable radiation information is restored, and the results are in accordance with the simulation.