With the popularization of electronic products, the electromagnetic compatibility problem of electronic equipment is more and more prominent. The suppression of electric fast transient burst (EFT / B) generated by switching power supply is an important research content. Based on the principle of EFT / B, this paper analyzes the basic principles and methods of EFT filter design, and uses the "negative parameter cancellation method" to deal with the design of the filter according to the parasitic parameters of the components that make up the filter Sexual adjustment, to achieve effective suppression of EFT / B noise purposes.