The invention discloses a preparation method for silicon oxide nano-particles, which comprises the following steps of preparing organic solution of alkoxy silane with an organic solvent; adding acid into the organic solution of the alkoxy silane and then putting into a microwave chemical reactor for reacting for 2-30 minutes so as to obtain organic solution of acidic alkoxy silane, wherein the temperature is 30 DEG C-180 DEG C, and the speed of stirring is 100rpm per minute-2000rpm per minute; adding surface modifier into the organic solution of the acidic alkoxy silane and then putting into the microwave chemical reactor for reacting for 2-30 minutes, wherein the temperature is 30 DEG C-180 DEG C, and the speed of stirring is 100rpm per minute-2000rpm per minute; reserving residue after centrifugation; and washing and drying the residue so as to obtain the silicon oxide nano-particles. The reaction speed of the preparation method for the silicon oxide nano-particles is ten or even thousand times that of a conventional method, the phenomenon of particle convergence is reduced, the particles are limited to grow, and the granularity is easy to control and is uniform.