The invention relates to a method for preparing tows for blended modified polylactic acid cigarettes. Fiber grade polypropylene particles, functional master batches and polylactic acid particles are uniformly mixed according to a certain ratio, and the tows for polylactic acid cigarettes are prepared through the working procedures of spinning, oiling, drafting, wrapping and drying. The method has a simple process and high speed to form, the produced product can reduce the specific weight of polylactic acid fiber, the operational performance is increased, the surface area of the fiber is increased, grain phase particles in smoke can be effectively absorbed, and a good filtering effect is generated.