The utility model discloses a transmission line iron tower rag bolt protective cap. Because the improper more potential safety hazard that exists is cast to the protective cap, very big degree ground is influencing transmission line's safe operation at present. The utility model discloses a characterized in that, connect one in rag bolt's the screw thread section and press the fixed cover of central point on the second nut, the fixed cover of central point, second nut, first nut and flat pad overcoat have a protective housing, the open -top of this protective housing, press on the tower base board bottom, there is 2 -10mm's space between the outer end of the fixed cover of central point and the inner wall of protective housing, is full of in the interior cavity of protective housing and solidifies the filler fast. The utility model discloses a protective cap has the bolt waterproofly, and isolated air prevents the effect of bolt oxidation, and the protective cap solidifies the back, also possesses the function that prevents the rag bolt upper cap nut and lose.