The invention discloses an ultrasonic sand grinding bed. The ultrasonic sand grinding bed mainly comprises a positioning frame, an input driving bevel gear shaft, an output driven bevel gear shaft, aninput gear shaft frame, an input driven bevel gear, a driving reducing gear, an output gear shaft frame, a driven reducing gear and an output driving bevel gear. Stepless speed changing is achieved through the manner of changing the combining radius of the driving reducing gear and the driven reducing gear. Ultrasonic waves are utilized for casting sand grinding, noise is avoided in the sand grinding process, energy consumption is extremely low, a casting is not damaged, the sand grinding speed is high, the effect is good, and the dead angle is not left. The same equipment can be used for castings different in size and dimension, component replacement is not needed, and a plurality of types of devices do not need to be prepared for the castings different in size and dimension