The invention discloses an edge-trimmed composite back sealing layer structure used for a silicon wafer. The edge-trimmed composite back sealing layer structure comprises a polysilicon back sealing layer and a silicon dioxide back sealing layer, wherein the polysilicon back sealing layer covers the back surface, back surface bevel edge regions and fringe regions of the silicon wafer; the silicon dioxide back sealing layer covers the polysilicon back sealing layer and is positioned on the back surface of the silicon wafer. According to the edge-trimmed composite back sealing layer structure used for the silicon wafer, only monocrystal silicon serving as a body material is left on the front surface bevel edge of the silicon wafer, and the front surface bevel edge has a smooth surface with high quality, which makes almost no difference from a polished surface. Only the monocrystal silicon layers are grown on the front surface bevel edge of the silicon wafer and the polished surface in epitaxial processing, seamless connection can be achieved, the layered phenomenon cannot occur, and the problems of particle contaminant, edge stacking fault and pyramid in epitaxial processing can be solved, thereby increasing the yield in manufacturing process.