A digital reordering unit, an ultrasonic front-end device and operating method thereof are provided. The ultrasonic front-end device may be connected between a probe and a detector of the ultrasonic system and controlled by a primary controller of the ultrasonic system; the ultrasonic front-end device having an ultrasonic transmission part and an ultrasonic reception part, wherein the ultrasonic transmission part includes a transmission beamformer and M transmission driving units, and has M transmission channels; the ultrasonic reception part includes M high-voltage isolation circuits, RC amplifiers, RC ADCs and a beamformer electrically connected in said order and has RC reception channels, where RC=[N,2N,3N . . . p*N], N being an integer larger than or equal to 1, being characterized in that, M low-voltage analog switches and a network of resistors are serially connected between the M high-voltage isolation circuits and the RC amplifiers.