The invention discloses a welding robot for machining of a pressure container. The welding robot is characterized by comprising a base, two pairs of supporting rollers arranged on the base, a driving motor for driving the supporting rollers, a walking device with lifting and horizontal displacement functions, a welding device mounted on the walking device and an electrical control device. The welding robot has the beneficial effects that the walking device capable of achieving the lifting and horizontal displacement functions meets the welding requirements for different portions of the pressure container, automatic welding is achieved under the automatic control operation, the welding efficiency is improved, the welding quality is ensured, and welding work becomes simpler and efficient.