An electro-isolation method was developed to address the stubborn issue of galvanic effect. This new technique is utterly different from any traditional corrosion-prevention methods in engineering. It simply applies a current to isolate the galvanic current, and thus it does not need to have a coating to cover the galvanic couple surface, to physically cut off the electronic path, or to insert an insulating separator (or spacer) to lengthen the ionic path. This paper comprehensively illustrates the unique principle of the isolation method, and reports on the experimental results showing that the electro-isolation did effectively retard the galvanic currents of various galvanic couples in different conditions, including the severe galvanic corrosion of Mg/steel couple in salt spray. The electro-isolation does not need a direct electronic connection with the galvanic corrosion system, and there is no risk of over-protection compared with the traditional cathodic protection. The innovative principle of the electro-isolation may trigger studies on micro and macro measurements and controls in other fields in future.