Provided is an ultrasonic inspection system of a vertical connection pipe inner wall of a steam generator of a nuclear reactor, which comprises a carrying platform (1), an ultrasonic inspection device (2) and a quick connection mechanism (3), wherein the carrying platform (1) is fixed in a manhole of a cold end water chamber of the steam generator, and realises quick connection and disconnection with the ultrasonic inspection device (2) through the quick connection mechanism (3); the carrying platform (1) can drive the ultrasonic inspection device (2) to lift and swing in a water outlet connection pipe of the steam generator, and realises ultrasonic inspection with respect to the water outlet connection pipe and an inner wall of a main pump connection welding seam; the carrying platform (1) can quickly mount the carrying platform (1) and the ultrasonic inspection device (2) outside the cold end water chamber of the steam generator; the ultrasonic inspection device (2) can be sent into an inspected connection pipe by means of the carrying platform (1); and the ultrasonic inspection device (2), by means of the movement of a plurality of its own mechanisms, can realise positioning and mounting in the inspected connection pipe, and can realise circumferential and axial ultrasonic inspection.