Disclosed herein is a robot mechanism for inspection of a live-line suspension insulator string. A robot body of the robot mechanism reciprocates along the live-line suspension insulator string and includes upper and lower robot frames configured to encircle the insulator string, a battery module provided to either end of the robot body, an actuation module for moving the robot body along the insulator string, an inspection module for electrically inspecting an insulator, a connection module for coupling the robot body to an installation/dismantlement mechanism, a wing opening/closing module for manually separating the robot body from the insulator string, a measurement module for measuring electrical properties of the insulator, a controller for controlling operation of the robot body, and a crack detection unit for detecting cracks formed in the insulator.