Abstract: In cutters of SQ3A series,pneumatic clutches are installed at the front end of band driving system to quickly disengage the driving motor from transmission system of bands when the machine is stopping,which effectively prevents the generation of narrow tobacco strands.The problem of narrow strands has been well solved in imported and new cutters of SQ341-244 and NQ11-13 series by incorporating servo control system,the working conditions for pneumatic clutches in tobacco cutter were analyzed by establishing mathematical models and calculating measured data.The results show that:1) it is necessary to install pneumatic clutches at the output end of band driving system to avoid the generation of narrow strands;2) if the band driving motor can be stopped by a control system within a very short time,pneumatic clutches are dispensable.