Abstract: To prevent the packet opening and packet deformation, a blank prefolding device was designed for YB48 hard packer. The device consisting of a cap prefolding mechanism and an external side panel prefolding mechanism is configured to mitigate the blank's stiffness at the folding lines. The cap prefolding mechanism consists of three parts that are installed respectively at station 4, station 5 and station 6 of the turret. The external side panel prefolding mechanism includes an improved spiral folding mechanism and folding assemblies fixed at the pentagonal wheel. By theoretical resilience analysis, it was determined that the prefolding angle for both mechanisms is 40°. The designed device was tested on cigarette brand "Baisha (Jingpin)" in Changsha Cigarette Factory. The results showed that the application of the designed prefolding device raised the operation efficiency of YB48 hard packer from 75.5% to 86.2%, reduced the number of cigarette packets with defective label from 184.2 to 28.6 packets per day, and the frequency of machine failure due to blank jam decreased from 16 times to 5 times per day. This technology provides technical support for improving cigarette production efficiency and packaging quality of cigarette packets.