Abstract: To solve the problem of thermal deformation during the cut-off process of polylactic acid (PLA) filter rods for heated tobacco products (HTPs), a vortex tube was added to the cut-off unit of filter rod maker to cool the cut-off knife. By numerical simulation, the preferable parameters of the vortex tube were determined: inlet pressure P_in 0.5 MPa, inlet air temperature T_in 26.85 ℃, the air flow leaving the vortex tube is divided into hot and cold streams. When the hot end air pressure P_hot is fixed at 0.07 MPa, the maximum cooling effect can be achieved. The vortex tube cooling was tested on an AF-KDF2 filter rod maker. The results showed that the temperature of the cut-off knife was lowered from 57.8 ℃ to 13.1 ℃, the fibrous tail at filter's cut end was avoided, meantime, the running speed of the maker was increased from 50 m/min to 150 m/min. The roundness and circumference of the filter rods were stably within the specified limits. This technology supports the improvement of HTP quality.