The invention relates to a device for detaching a multi-segment oil drill pipe. The device comprises a hydraulic base, a hydraulic cylinder, a clamping ring and fixing devices, wherein the clamping ring comprises two semicircular snap rings which are arranged symmetrically; the snap rings are provided with open ends and enclosed ends; the enclosed ends of the two symmetrical snap rings are connected through a hinge; connecting plates are arranged at the open ends of the two snap rings; the connecting plates are provided with threaded through holes which are matched with a screw rod and a screw cap; the inner walls of the snap rings are provided with threaded surfaces; a plurality of fixing blocks are uniformly arranged on the outer walls of the snap rings. According to the device, the clamping ring is set into two symmetrical semicircular snap rings, the enclosed ends of the two snap rings are connected through the hinge, and the open ends of the two snap rings are connected by matching the screw rod with a screw, so that the open ends of the snap rings can be opened and closed freely, a drill rod can be inserted conveniently, and the problem of difficulty in operating during insertion of the drill rod into a clamping portion of the conventional detaching device is solved.