In this work, digital light processing (DLP) 3D printing technology was used to fabricate transparent silica glass with complex structures. The effects of different particle sizes and mixing ratios of silica powders on the viscosity of the prepared slurries were investigated. The results showed that when 100–200 nm and 800 nm silica powders were mixed in a 1:4 vol ratio, the slurry exhibited the lowest viscosity. The highest solid loading of the slurry prepared with this mixed silica powder reached 75 wt%, with a viscosity of only 1245 mPa·s. The high solid loading slurry was subjected to 3D printing, debinding, and sintering treatment, and the transparent silica glass samples with complex structures was obtained.