The invention discloses an automatic turn-over device for long-roll sock legs and a control method. The automatic turn-over device comprises a sock tube fixed to a rack, and further comprises a feeding compression mechanism, a chain driving mechanism, a lifting air suction mechanism, a material collecting winding roller mechanism, a mechanical arm mechanism, a sock head clamping mechanism, a detection sensor set, an automatic binding machine and a control cabinet. According to the automatic turn-over device, in the feeding process, the return speed of the feeding compression mechanism and therunning speed of a conveying belt are controlled according to the load torque change of a servo motor, the quality of sock materials is guaranteed, and meanwhile the long-roll sock legs with differentthicknesses and different lengths can be stacked on the sock tube; and in the material turning process, automatic identification and automatic binding of sock heads and sock tails are achieved in combination with detection of the detection sensor set and cooperative action of the lifting air suction mechanism, the material collecting winding roller mechanism, the sock head clamping mechanism andthe automatic binding machine. According to the automatic turn-over device, the processes of automatic feeding, automatic overturning, automatic head and tail recognition and bundling and precise conveying of a mechanical arm after manual sock sleeving can be achieved, the labor intensity is reduced, the sock product quality is effectively guaranteed, and the reliability and the production efficiency are improved.