The invention discloses an ascent-free automatic scrubbing device for an insulator. The ascent-free automatic scrubbing device for the insulator comprises a support arranged at the upper end of a supporting rod, locking mechanisms capable of being in locking fit with the two end portions of the insulator are arranged at the two ends of the support, a semi-ring rail capable of going up and down is arranged on the support through a lifting mechanism, a semi-ring sliding block capable of rotating around the axial line of the semi-ring rail is arranged on the semi-ring rail in a sliding mode, brushes corresponding to the outer wall of the insulator are arranged on the inner ring wall of the semi-ring sliding block, a scrubbing motor is arranged on the lifting mechanism, a driving gear is arranged on the output shaft of the scrubbing motor, gear teeth meshed with the gear are evenly distributed on the outer ring wall of the semi-ring sliding block, lugs are fixedly arranged at the two ends of the semi-ring sliding block, a position sensor matched with the lugs is arranged in the middle of the semi-ring rail, and the ascent-free automatic scrubbing device further comprises a controller controlling the scrubbing motor to rotating forwards and backwards automatically according to the signals of the position sensor. The ascent-free automatic scrubbing device for the insulator has the advantages of being capable of assisting the cleaning of the insulator without the needs for ascent, free of cleaning dead angles, good in cleaning effect, capable of saving time and labor in cleaning, low in cost and beneficial to improving scrubbing efficiency.