The invention discloses an ultrasonic wave-based coal dust concentration dynamic detection system and coal dust concentration dynamic monitoring method of mine. Sixteen ultrasonic sensors are fixed on the inner wall of an inner ring in a uniform angle manner, and every ultrasonic sensor simultaneously has ultrasonic wave emitting and receiving functions; all signal wires are commonly connected to a multi-core plug on an outer ring, the multi-core plug is connected with a programmed multipath toggle switch through a shielded multi-core cable, the programmed multipath toggle switch is respectively connected with a voltage pulse generator and an ultrasonic data acquisition device through wires, the voltage pulse generator is connected with the ultrasonic data acquisition device through a wire, and the ultrasonic data acquisition device is connected with a data processing center through a wire. An existing single-emitting and single-receiving detection mode is improved to a cycle single-emitting multi-receiving CT detection mode, and an ultrasonic wave speed CT image and an absorption coefficient CT image are adopted to reflect the coal dust concentration distribution, so the detection accuracy is improved.