Modern medical devices are more inclined to high precision, high sensitivity, and miniaturization, resulting in more and more complex electromagnetic environments. External electromagnetic interference will also affect medical devices, and even affect doctors' diagnosis in severe cases. In this paper, combined with the heart sound electrocardiograph detector, the conduction emission test, radiation emission test and electrostatic discharge test are studied based on the medical device test standard. Some rectification methods are proposed, such as rectifying the shell, adding the filter circuit, adding the magnetic ring and adding the charge release circuit. It can be used as a reference for the analysis and rectification of other types of related medical devices.