The invention relates to an insulation structure of wrench, specifically to an insulation structure of wrench with good protection effect. A wrench head of the wrench comprises a shell body; an insertion part is exposed on the outside of the shell body; an insulation layer comprises an insulation shell and an insulation sleeve part; while the insulation shell covers the outer surface of the shell body, the insulation sleeve part integrated with the insulation shell surrounds the insertion part; the insulation sleeve part is combined with an insulation loop; a combining section extends from the insulation loop along the inner wall of the insulation sleeve part; the insulation loop is provided with a connecting seal edge at the inner end of the combining section, the connecting seal edge converging towards the insertion part; and an insulation bush extends outward from the inner edge of the connecting seal edge in the axial direction of the outer wall of the insertion part. The insulation sleeve part is combined with the insulation loop, the insulation loop can be detached according to requirements for maintenance of the head of the insulation wrench and an insulation effect for preventing electric leakage is achieved.