The present invention discloses a protection element. The protection element comprises: a ceramic substrate; a heating body arranged at the upper portion or the lower portion of the ceramic substrate;a main conductive loop, or called as a fuse part, arranged at the upper portion of the heating element, wherein after a certain current flows through the heating element, the main conductive loop canbe fused and an open circuit is formed; an auxiliary fusing agent arranged at the upper portion of the main conductive loop (fuse part) to help the main conductive loop (fuse part) to fuse more quickly and uniformly; a shell arranged on the substrate and forming a certain space with the substrate, wherein a heating layer and the main conductive loop are both arranged in the space; a fourth port connected with the outside in a different connection mode from other three ports, wherein the fourth port is in open-circuit with the three ports. The protection element has the appearance basically equal to the prior conventional protection element, can be directly replaced with the conventional protection element, but has the purpose of playing the normal overvoltage protection function even if the mounting is wrong.