The invention discloses an autonomous navigation method and system of a high-voltage transmission line inspection robot. The method comprises two working modes: overall autonomous navigation and localautonomous navigation; the initial working mode is set as the overall autonomous navigation mode; the method comprises the following steps: receiving the robot current state information and the surrounding data collected in real time during inspection; determining the current position and current environment of the robot according to the current state, the surrounding data and a GIS power transmission line information database; judging whether to transfer into the local autonomous navigation mode according to the current position of the robot; if so, reducing speed in advance, transferring into the local autonomous navigation mode; after the work in the local autonomous navigation mode is finished, adjusting the motion parameters according to the current position of the robot; adjusting the motion parameters of the robot according to the current environment. The method and the system disclosed by the invention can guarantee the robot safety on the premise of realizing high-efficiencyinspection.