Abstract: In view of problem of low measurement accuracy when traditional electric equipment measures formation with big resistivity, the paper proposed a scheme of using digital cross-correlation technology to reduce noise in AC electrical equipment. The scheme makes AD conversion for measuring signal of receiving electrode of AC electrical equipment and reference signal of exciting source, and calculates cross-correlation function of the measuring signal and the reference signal in DSP processor to extract useful components in the measuring signal which has the same frequency with reference signal, so as to effectively filter various noises in signal transmission process. Test result shows that using digital cross-correlation technology to process weak measuring signal of AC electrical equipment can improve measuring precision and anti-interference ability of AC electrical equipment.