The invention relates to an optical fiber longitudinal stripping device. The device comprises a frame. An upper portion of the frame is provided with an air cylinder. The frame below the air cylinder is provided with two sets of clamping devices. The two sets of clamping devices are arranged symmetrically. A piston rod of the air cylinder is connected to a first movable plate of two sets of clamping devices through a first connection board. A lower portion of the frame is connected to a knife holder through a second connection board. The knife holder is located at a position which is between a first pulley and a second pulley and is below the first pulley and the second pulley. A screw passes through the knife holder and is connected with a screw thread. An upper end of the screw is provided with a stripping knife. A lower end of the screw is provided with a nut. The screw is provided with a pointer used for displaying a stripping knife moving distance. The pointer corresponds to a graduation line on the frame. A position on the frame, which corresponds to the position between the first pulley and the second pulley, is provided with a through hole. The structure is designed reasonably and usage is convenient. An optical fiber is fixed firmly. A phenomenon that an optical cable slides leftwards and rightwards because of uneven stress during a stripping process is avoided and a cutting depth of the stripping knife can be accurately controlled.