The invention discloses a screening bottom frame cleaning device for an ultrasonic vibrating screen. The device comprises a motor which is arranged inside an ultrasonic vibrating screen and is connected with the bottom of a screening bottom frame through a motor base, wherein the motor is connected with the bottom of a connecting shaft; a blind hole is formed in the surface of the top of the connecting shaft, and an upper end cover is arranged at the blink hole; a through hole is formed in the upper end cover, and two ends of the through hole are respectively connected with a pipeline and the blind hole; the pipeline runs through the side wall of the ultrasonic vibrating screen and is connected with an air compressor; a hollow connecting rod is arranged on the side face of the connecting shaft; one end of the connecting rod is communicated with the blind hole, and the other end of the connecting rod is provided with an end cover; air is blown into the screening bottom frame constantly through a blowing hole, and a material cleaning device is driven by the connecting rod to constantly scratch materials adhered to the screening bottom frame, so that the materials adsorbed on the screening bottom frame can be cleaned and removed conveniently and efficiently.