The utility model discloses a flexible intelligent ultrasonic sealed cleaning device which comprises a flexible shell capable of being arranged on a main transformer radiator in a sleeving manner and a control circuit. The flexible shell is formed by clasping both front and rear halves; the front and rear halves are locked by a waterproof zipper or a concave-convex seal groove; a plurality of ultrasonic probes are embedded on the flexible shell; the shell is provided with a water inlet and a water outlet which run through the inner and outer walls of the shell; a water inlet electromagnetic valve is arranged at the position of the water inlet; a water outlet online conductometer and a water outlet valve are arranged at the position of the water outlet; the ultrasonic probes are connected with an ultrasonic generator; the control circuit monitors the conducting condition of cleaning fluid at the water outlet by the online conductometer and controls the ultrasonic generator and the water inlet electromagnetic valve to work. According to the device, no dead angle can be left, the water bloom splashing phenomenon cannot be generated, uninterrupted online cleaning is implemented, and the problem of safely, efficiently, cleanly and rapidly washing the main transformer radiator under the live running condition of a main transformer is completely solved.