The invention provides high-boron high-chromium low-carbon high-temperature-resistant wear-resisting alloy steel and manufacturing method thereof. The chemical content of the alloy steel includes, by weight, 0.10%-0.5% of C, 3%-26% of Cr, 0.5%-4% of W, 0.5%-1.2% of Si, 0.5%-1.5% of Mn, 0.7%-3.5% of B, 0.3%-2.6% of Cu, 1.5%-2.4% of Al, 0.8%-1.6% of Ti, 0.02%-0.15% of Ca, 0.03-0.25% of Ce, 0.02%-0.18% of N, 0.05%-0.3% of Nb, 0.12%-0.25% of Mg, 0.04%-0.13% of K, 0.05%-0.12% of Ca, 0.06%-0.15% of Ba, less than 0.03% of S, less than 0.04% of P and the balance Fe and unavoidable impurity elements. After steel scrap and ferrochromium are melted in an electric furnace, a copper plate, silicon iron and ferromanganese are added to the electric furnace, after content is qualified through pre-furnace adjustment, the temperature of a melt rises to 1560-1620 DEG C, calcium-silicon alloy and deoxidation aluminum are added, ferrotitanium, ferroboron and metal aluminum are sequentially added and poured out of the furnace after being melted, granular rare earth magnesium alloy with a diameter of less than 12mm and a composite inoculant composed of metal cerium, Si3N4, VN, Nb and K are placed at the bottom of a steel ladle after being roasted, metaphoric inoculation processing is carried out on smelt liquid steel in a in-ladle pouring mode, the liquid steel pouring temperature ranges from 1400 DEG C to 1450 DEG C, and a casting piece undergoes air cooling for 2-4 hours at the temperature of 920-1150 DEG C.