Abstract: In order to reduce accidental machine stop caused by cigarette carton misalignment and squeezing in the process of case filling, a flexible case compressing device was added to YP11 case filling and sealing machine to restrict the inertial movement of cigarette cartons via compressing the upper space of the case. Through experiments, it was found that a compressing brush made of hog bristles with the dimension of 176 mm×28 mm was preferable and there was no indentation remained on the case and cartons when the brush pressed on the central position of case's upper wall to make it moving downward by 7 mm with a force larger than 60.1 N, the inertial sliding distance of cigarette cartons at the first layer was less than 3.2 mm, and no cigarette carton misalignment and squeezing happened. Cigarettes of brand "Yan'an (Soft)" were tested in Yan'an Cigarette Factory, the results showed that the accidental machine stop caused by cigarette carton misalignment and squeezing reduced from 29 times/month to 0. This design provides a support for promoting the appearance quality of cigarette products.