The PCB board of automotive circuit electromagnetic compatibility (EMC) rectification is increasingly demanding for limited space, requiring convenience and efficiency, and on-site rectification must shorten time and reduce costs. On the basis of the traditional classical LC filter commonly used in EMC rectification, the zero points of some frequency points in the stopband of the filter are obtained by transforming the capacitive or inductive components of the series branch into the LC parallel resonant circuit, and the position and depth of the stopband zero point can be adjusted by the capacitive or inductive value and Q value of the resonant circuit respectively, which greatly increases the stopband suppression, and a wide range of high stopband suppression can be realized without greatly increasing the order of the LC filter. A transformed improved LC filter is designed and debugged successfully through simulation optimization. The improved filter has the advantages of miniaturization, low loss, high rejection, adjustability and low cost. Compared with the traditional classical LC filter, the insertion loss at the cutoff frequency of the passband is only 0.79 dB worse, and the stopband suppression at the near-end frequency of the stopband is increased by 31.5 dB. The stopband suppression at the frequency of 968.4 MHz is improved by 22.4 dB, and the rectification process has the characteristics of reliability, simplicity and rapidity, which can be applied to the EMC over-standard rectification of automobile circuits in the corresponding frequency bands of common national standards GB 34660-2017 and GB/T 18387-2017.