The invention relates to a composite wire for linear cutting. The composite wire comprises a metal wire as a basal body, and a wear-resistant resin layer coated on the outer surface of the metal wire;the metal wire comprises the following chemical components in percentage by weight: 0.70-1.0 of C, 0.20-0.40 of Cr, 0.30-0.50 of Mn, 0.15-0.20 of Zr, 0.02-0.08 of W, Ca not more than 0.010, B not more than 0.020, N not more than 0.006, and the balance of Fe and inevitable impurities; and the wear-resistant resin layer is prepared by the following raw materials: 15-25 parts of surface-modified chromium oxide, 30-60 parts of unsaturated resin, 10-15 parts of carbon fiber, 100-200 parts of tetrahydrofuran, and 0.5-1 part of initiator. The invention provides the composite wire for linear cuttingand a preparation method thereof; and the composite wire is high in wear resistance and cutting efficiency, high in mortar carrying quantity, low in cutting cost and accordant with the performance requirements on wires for multi-line cutting.