Abstract: Taking mine-used multi-function control driver as an example, the paper proposed an optimization scheme to suppress conducted EMI noise of single-chip microcomputer. The scheme can diagnose and suppress conducted EMI of device according to generating mechanism of conducted EMI noise. It gets common-mode component and differential-mode component through extracting modal of conducted EMI noise of single-chip microcomputer. Meanwhile, it detects internal impedance of noise source to design corresponding EMI filter to suppress conducted EMI noise of the single-chip microcomputer combining with corresponding noise modal. The practical application indicated that the scheme can suppress total conducted EMI noise of single-chip microcomputer effectively.