A cellulose acetate particle aggregate, a preparation method therefor and an application thereof, which relate to the field of harm reduction additives in cigarettes. The cellulose acetate particle aggregate includes 49-99.5 wt % of cellulose acetate particles, 0-50 wt % of a second kind of particles, and 0.5-20 wt % of a binder. The preparation method involves selecting cellulose acetate particles and a second kind of particles in a certain ratio, or cellulose acetate particles alone, preparing particle aggregates by using an air fluidized granulation method while adding a binder thereto, and sieving the particle aggregates to obtain a cellulose acetate particle aggregate having a required particle size. The cellulose acetate particle aggregate has a porous structure, an irregular shape, and a rough and uneven surface, which help to improve the efficiency of filtering out particulate matters or one or more harmful ingredients in cigarette smoke.