This paper designs a flight-sliding inspection robot which has the function of flight and on-line inspection, this machine combines the advantages of four-rotor and inspection robot, sliding on the zero line of transmission line for inspecting. The control method and overall structure are discussed in detail, designed the PID control with dead zone for self-balancing online. As well, the hardware platform are built, finally achieve self-balancing online of flight-sliding inspection robot. The experimental results verify the feasibility of this method.