The invention discloses a preparation method of nano glass powder. The preparation method comprises the following steps of firstly, uniformly mixing multiple kinds of glass raw materials to form a mixed glass raw material, wherein the glass raw materials comprise one or several kinds of nonmetallic oxides, alkaline earth metal oxides or alkali metal oxides; secondly, melting the mixed glass raw material to form liquid glass; thirdly, performing water quenching on the liquid glass by using a water quenching liquid in a highly turbulent state to form a glass suspension; fourthly, drying and collecting the glass suspension to obtain the nano glass powder. According to the preparation method disclosed by the invention, the nano glass powder is prepared by using a method of water quenching, high cut disperse and centrifugal spray drying; compared with a traditional preparation process, the preparation method has the advantages of short preparation process and high yield; the prepared nano glass powder is high in purity, small in particle size, uniform in particle size distribution and good in dispersion, and can be applied to conductive slurry in the fields of microelectronics and solar cells.