Abstract: In order to study the principle and characteristics of the cutoff system in new type cigarette makers, a mathematical model of the four-linkage rotary ledger mechanism in the cutoff system in PROTOS M8 cigarette maker was derived on the basis of mathematical analysis. The movement relationship between cutoff knife and ledger during cutting was analyzed and calculated, the theoretical errors of the system were taken into account, and the design parameters of the cutoff system were optimized. The results showed that the deviation between knife and ledger should not exceed 0.05 mm;and the inclination angle of cutoff knife carrier and the rotation diameter of ledger corresponding to cigarette length should be accurately calculated and corrected in design, the optimized rotation diameter of ledger should be:theoretical value+(0.2-0.4)mm and the optimized inclination angle of cutoff knife carrier should be:theoretical value+0.1°. The calculation results provide a theoretical reference for the development of new type cutoff system.