The invention discloses a 
silicified microcrystalline cellulose composite auxiliary material and a preparation method thereof, belonging to the field of medical premixed composite auxiliary materials. The 
silicified microcrystalline cellulose composite auxiliary material disclosed by the invention consists of the following components in parts by 
mass: 25.2-25.5 parts of 
microcrystalline cellulose, 0.5-0.8 part of 
silicon dioxide, 0.08 part of hydroxypropyl methylcellulose K4M and 74 parts of water. The preparation method comprises the following steps: (1) dissolving the hydroxypropyl methylcellulose K4M and water, adding the dissolved substances into a stirrer, adding the 
silicon dioxide, stirring, adding the 
microcrystalline cellulose, and stirring, thereby obtaining uniform suspension A; (2) setting the air 
inlet temperature at 160 DEG C by using a centrifugal 
spray dryer, setting the outlet temperature at 95 DEG C, setting the rotating speed of an atomizer at 8000 
revolutions per minute, setting the rotating speed of a 
peristaltic pump at 20 
revolutions per minute, and 
drying, thereby obtaining a material B; (3) adding the material B into a screening 
machine, vibrating and screening to the 
granularity of 80 meshes, thereby obtaining 
sieve residues C; and (4) testing the samples of 
sieve residues C, thereby obtaining the product of which the quality accords with the regulation, namely the composite auxiliary material. According to the composite auxiliary material and the preparation method thereof provided by the invention, the requirement of directly pressing the 
powder is met, so that the product is uniform in tablet weight, large in tablet 
hardness, smooth in tablet and qualified in 
dissolution rate.