The square parts, with manual bilateral chamfering, are low efficiency and poor consistency.The square parts automatic bilateral chamfering machine, developed with modular design method, can achieve a certain range of square parts automatic bilateral chamfering, and can adjust the cutter location to adjust bilateral chamfer amount of the work piece,realizing consistency.The system composition and module partition,chamfering machine movement scheme,and some key parts design were introduced.It is verified by the prototype experiments that the chamfering machine can reach the expected effect.