The invention discloses a method for preparing large-size yttrium-system block materials by using an Ag2O-added YBCO solder braze welding method, and belongs to the technical field of superconductive block material preparation. The method is to adopt a top-seeded melt-textured growth method to prepare Ag2O-added YBCO solder, adopt braze welding connecting technology to weld YBCO block materials, perform post-oxidation treatment on braze welding joints, restore the superconductivity of a YBCO braze welding sample, and obtain yttrium barium copper oxygen superconductive block materials. The invention adopts the braze welding method to prepare the YBCO superconductive block materials which have large size and complex shape and cannot be prepared by the prior method, and the YBCO superconductive block materials have similar superconductivity with single-domain block materials prepared by the top-seeded melt-textured growth method. Because developed solder compositions are similar to the chemical compositions of the prior base metal, the texture of soldering seams is similar to that of the base metal. The superconductivity of the YBCO high-temperature superconductive block materials prepared by the method can reach more than 60 percent of the prior block material.