Abstract: The malfunction of cut-off knife feeding in PROTOS 70 cigarette maker is often resulted from the air leak of seal ring or bearing damage in its knife feed mechanism, which deteriorates the quality of cigarette cutting. Therefore, the mechanism was improved as following: replacing the built-in non-standard cylinder with an external standard cylinder; the mechanism was then composed of two independent units, a cylinder type pusher and a mandril mechanism which linked to the external cylinder via a bearing. The results of application showed that the modification improved the working stability and reliability of the knife feed mechanism, and completely solved the frequent failures of the same, and the frequency of maintenance and cost of spare parts decreased by 75% and 99%, respectively.