The invention discloses a method for preparing fused silica bricks and belongs to the technical field of refractory materials. The method is characterized by comprising the following preparation steps: dosing, mixing, hydro-forming, drying and firing, and the fused silica bricks comprise the following components in parts by weight: 32-38 parts of 1-3mm high-purity fused silica sand, 13-17 parts of0.3-1mm high-purity fused silica sand, 32-38 parts of 200-mesh high-purity fused silica sand, 2.5-3.5 parts of a silica gel binder, 2.5-3.5 parts of silica powder, 1.7-2.3 parts of phosphoric acid and 6-8 parts of a high-temperature adhesive; and the firing temperature is as follows: the temperature is maintained at 195-205 DEG C for 7.5-8.5 hours, and continuously raised to 985-1004 DEG C to bemaintained for 3.5-4.5 hours. The low thermal expansion fused silica brick prepared by the method disclosed by the invention has excellent heat resistance, is adaptive to a drastic temperature change,and has the most major advantage that the fused silica brick can be heated in a short time after masonry and does not produce thermal expansion after being heated, so that thermal expansion calculation does not need to be performed, and cold masonry can be performed according to a thermal size.