Abstract: By calculation and experiment, it was found that the value of correct coefficient (K) in formula for tobacco cut width calculation given by LEGG Company was too big, which resulted in a narrower practical cut width with a deviation of 8% from the design value. The variation of cut width was caused by the linear velocity difference between the top and bottom bands in RC4 cutter. The value of K was changed from 0.52 to 0.48, and the worm gear transmission ratio of top band increased by 22.1%. After improving, it was ensured that the sectional velocity of tobacco leaf coming out of the mouthpiece was the same.