The invention provides a preparation method of non-spherical silica sol. The method comprises steps that: (1) a non-spherical silica sol crystal seed mother liquor with a particle size of 20-50nm is prepared; (2) water-soluble silica sol with an alcohol content lower than 5wt% is prepared. The method provided by the invention has technical effects that: a sol-gel method is adopted; with process controls over material blending, material concentration, reaction liquid pH and reaction temperature during a reaction process, silica sol with a non-spherical structure is directly prepared. The method provided by the invention is advantaged in small amount of side reaction, short growing period, and simple technology. According to the method, no additive or inorganic salt is required to be added, and no surface modification process is required. The prepared silica sol can be used in a grinding and polishing process during a rough-polishing procedure in a CMP technology, and can be used as a carrier required in modification processes of other particles. In the non-spherical silica sol, content of spherical particles is lower than 5%. The particle size of the sol is controllable, and is 20-100nm. With an evaporation dehydration technology, the SiO2 content in the water-soluble silica sol is controlled at 5-50wt%.