A preparation method of cellulose aerogel balls with a controllable diameters comprises the following steps: 1) dissolving cellulose powder in a NaOH/urea system to obtain a cellulose solution; 2) mixing a certain proportion of chloroform and an acid or mixing ethyl acetate and the acid to obtain an acidic coagulation bath, and stirring to uniformly mix the coagulation bath; (3) transferring the cellulose solution into a dispensing syringe to enable the cellulose solution to fall into the stirred coagulation bath through a special nozzle under different pressures to obtain cellulose gel ballswith different diameters; 4) filtering the cellulose gel balls by suction, replacing the solvent and drying to obtain the cellulose aerogel balls. The cellulose aerogel balls prepared by the preparation method are nearly perfect spherical, have controllable diameters and uniform sizes, can greatly expand the application range of the cellulose aerogel, and have high preparation efficiency and cheapexperimental equipment. The particle sizes of cellulose aerogel balls can be adjusted within the range of 5 mu m to 2 mm, and cross-linked pores are mesopores and micropores.