The invention discloses a pipe cutting device for a self-positioning pipeline. The device comprises a rack, and further comprises multiple straightening devices, a cutting machine and a positioning device which are sequentially arranged on the top of the rack in the machining direction; the cutting machine comprises a cutting table, two clamping tables and a cutting disc; the cutting table is fixed to the rack, the two clamping tables are symmetrically mounted on the two ends of the cutting table, the cutting disc is arranged on the cutting table through a supporting frame, the positioning device comprises a support, a screw, a servo motor, a baffle and automatic clamping claws, the support is fixed to the rack, multiple air cylinders which are arranged in a hanging manner are arranged onthe support, the automatic clamping claws are arranged on piston rods of the air cylinders, and a material accumulating groove is formed in the position, below the support, of the rack. The cutting machine and the positioning device are arranged, the long pipeline can be precisely positioned and cut, machining efficiency is improved, the process of cutting the pipeline again on the later is removed, and raw material waste is reduced.