An inspection robot for 220 kV high-voltage transmission line is presented. Its characteristics are as follow. Firstly

it achieves the automatic motion on a live line (rolling

crawling and spanning obstacles) with the minimal freedom degrees

smart mechanical structure and the mixed reaction with multi-transducers and machine vision. Secondly

it can automatically supply the electrical energy for itself through current transformer technique. Last

it can detect and diagnose the malfunction of the lines with visible light and infrared imaging instruments

and has the function of management for the inspecting data and diagram information. The robot has passed the test on a field live line and demonstrates its broad application prospect.