The invention discloses Fe-Cr-B cast abrasion-resistant alloy and a manufacturing method thereof, the alloy comprises the following chemical compositions by mass percent: 0.22-0.45% of C, 12.0-18.0% of Cr, 0-8-1.5% of Si, 0-6-1.5% of Mn, 0-9-1.2% of B, 0.30-0.45% of Ni, 0.02-0.04% of Mg, 0.03-0.05% of Ce, 0.04-0.08% of Ti, 0.008-0.015% of N, 0.06-0.09% of Zn, less than 0.04% of S, less than 0.04% of P and the balance of Fe. After melting, casting and hot-processing, the hardness and toughness of the Fe-Cr-B cast abrasion-resistant alloy can be adjusted in a wide range so as to meet the requirements of different abrasion working conditions. The invention uses low-cost chromium and boron as the main alloying elements, does not contain expensive alloying elements such as tungsten, molybdenum, vanadium, niobium and the like, has the characteristics of high hardness, good toughness and the like, and has low cost, and has good economic benefit when being popularized.