Failed in knife feeding in SQ35 tobacco cutter is a frequent failure caused by damaged primary and secondary worm gear pair resulted from over-wide clearance between tension roller and its shaft or serious wear of tension roller's sliding bearing. The tension roller is modified by replacing sliding bearing with needle bearing and adopting pedestal oil ring to prevent lubricating oil from being contaminated, decrease friction and chain tension, as a result to reduce the failures of knife feeding mechanism, and ensure normal machine running and tobacco cutting. The practical application indicated that the frequency of parts replacing reduced from 43 to 12 times/year per machine, and the amount of cut tobacco not up to the standard caused by machine failures decreased from 2365 to 660 kg.