The invention belongs to the technical field of metallurgy, and provides a high-nitrogen composite alloy which is prepared from the following components in percentage by weight: 5 to 20 percent of nitrogen, 15 to 40 percent of titanium, 15 to 40 percent of niobium, 10 to 20 percent of chromium, 10 to 20 percent of silicon, 2 to 10 percent of manganese, 1 to 5 percent of rare earth lanthanum, lessthan or equal to 1.0 percent of carbon, less than or equal to 0.06 percent of sulfur, and less than or equal to 0.1 percent of phosphorus. A preparation method comprises the steps of premixing raw material, then mixing, rising temperature, pretreating, then rising temperature for three times under the vacuum condition, preserving heat, pressing and firing. According to the prepared high-nitrogen composite alloy, the nitrogen content is remarkably improved, and a reinforcing steel bar using the high-nitrogen composite alloy has high tensile strength and bending strength, good shock resistance,good toughness and excellent mechanical property. The high-nitrogen composite alloy provided by the invention solves the problems of instable quality and low nitrogen content of the high-nitrogen reinforcing steel bar in the prior art.