The utility model belongs to a high-low voltage isolation device, which is formed by a casing and a high-low voltage isolating circuit inside the casing. The main technical key points are that a non-linear element is respectively connected in parallel between two voltage input ends and between two voltage output ends, the two voltage input ends are respectively connected with two photoelectric couplers, and the two photoelectric couplers are respectively connected with the two voltage output ends. The utility model effectively solves the problem of endangering personal and instrument safety on a measuring terminal by conditions of intermittent overvoltage, chopped impulse overvoltage, and overvoltage generated by sudden rising of earth point electric potential in the process of alternating and direct current voltage endurance tests, and has the characteristics of fast response speed, timely protection, simple use and convenient implantation, and can be widely applied in the measuring loop of the alternating and direct current voltage endurance test.