The invention belongs to the technical field of power transmission line broken strand repairing, in particular to a power transmission line broken strand repair robot mechanism. The robot mechanism comprises a repairing tool, an electric appliance box, a forearm, a rear arm, a front walking device and a rear walking device, wherein the forearm and the rear arm are respectively disposed on the front and rear sides of the electric appliance box, and the tail ends of the forearm and the rear arm are respectively connected to the front walking device and the rear walking device. The repairing toolis disposed on the electric appliance box and is between the forearm and the rear arm. The robot mechanism can automatically repair broken strands, improve efficiency, reduce labor intensity of personnel and improve personal safety.