The invention relates to a device convenient to fix and used for detaching a multi-section type oil drill pipe. The device comprises a hydraulic base, a hydraulic cylinder fixed to the hydraulic base, fixing devices and a clamping ring. The clamping ring is arranged on the two fixing devices. A plurality of fixing blocks are arranged on the outer wall of the clamping ring. A plurality of grooves are formed in the clamping ring. Springs are arranged in the grooves. Clamping blocks are arranged at the upper ends of the springs. The top faces of the clamping blocks cave inwards to form cambered surfaces. The radian of the cambered surfaces is matched with the radian of the outer wall of the drill pipe. Threaded faces are arranged on the cambered surfaces. Baffles are arranged on the side walls of the grooves. By arranging the clamping blocks controlled by stretching out and drawing back the springs in the clamping ring and setting the top faces of the clamping blocks into the cambered surfaces with the radian matched with the radian of the outer wall of the drill pipe, the drill pipe can be well tightly clamped through the clamping blocks, and the problem that an existing detaching device is prone to sliding when tightly clamping the drill pipe is solved.