A 500kV transmission line insulator with a protective gap comprises an insulator, a grounding side gap electrode, a high-voltage side gap electrode and an accessory, wherein the grounding side gap electrode and the high-voltage side gap electrode are respectively arranged at the grounding side and the high-voltage side of the insulator, the distance from the gap to the axis of the insulator is no less than 400mm, the distance of the gap is in the range of 65%-95% of the structure height of the insulator, and the high-voltage side gap electrode also serves as a grading ring of the insulator. Paralleled gap is a channelized protection method different from a traditional lightning prevention measure, avoids the failure damage of the insulator, improves the success rate of reclosing, and avoids the occurrence of permanent fault. The 500kV transmission line insulator with the protective gap can protect the insulator from being damaged and ensures the reclosing to be successful, so that a lightning flashover becomes a transient fault, and normal power supply of a power grid is guaranteed; an original grading ring is replaced by the high-voltage side gap, so that the potential distribution of the insulator is more uniform; and the 500kV transmission line insulator with the protective gap is lighter and is easy to install.