Abstract: The ratchet wheel and pawl of automatic knife feed mechanism in PASSIM80 cigarette maker had to be replaced frequently because of serious wear.The feed mechanism was modified as following:1) the ratchet pair was replaced by an one-way overruning clutch;2) knife feeding was controlled by adjusting cylinder stroke and setting feeding time.The working life of knife prolonged from 7-8 hours to 30-40 hours, the maintenance period of feed mechanism prolonged from 1-2 months to 1 year, and the machine efficiency was improved accordingly.