The invention relates to a filament forming process for paper making method-based reconstituted tobacco and a device thereof. The invention is characterized in that the process comprises the following steps of: a. forming filaments by adopting a three-step slitting procedure, i.e. firstly slitting into slices, then slitting into strips, and finally slitting into filaments to carry out the filament forming step of the reconstituted tobacco; b. drying: feeding the reconstituted tobacco filaments having a water content of 16-20% to a drum type tobacco filament drier for drying by a constant feeder, wherein the water content of the dried reconstituted tobacco filaments is 11-13%; and c. blending: directly blending the dried reconstituted tobacco filaments in a tobacco filament production line according to the design proportion of a cigarette prescription. The process and the device can solve the problem that the paper making method-based reconstituted tobacco is difficult to make into filaments solely, raises the effective utilization rate of the paper making method-based reconstituted tobacco; and the made reconstituted tobacco filaments have uniform length, good bulking property, and effectively maintained fragrance, thereby improving the sensory quality.