Submarine pipeline welding seam polishing device and polishing method thereof

The invention discloses a submarine pipeline weld joint polishing device and a polishing method thereof, relates to the technical field of pipeline weld joint polishing, and aims to solve the problems that in order to meet the polishing requirements of internal and external weld joints, an existing device needs to erect guide rails inside and outside a pipeline firstly, and internal and external weld joint polishing can be completed by means of a rail trolley; the construction difficulty is high, and time and labor are wasted. The self-moving trolley is arranged below the inner seam polishing mechanism, wheels are installed on the two sides of the self-moving trolley, and the number of the wheels is four; the first hydraulic rod is installed at the upper end of the self-moving trolley, a double-end hydraulic cylinder is installed at the output end of the first hydraulic rod, and arc-shaped stabilizing frames are installed at the output ends of the two sides of the double-end hydraulic cylinder; and the motor