A method for manufacturing a low-carbon nitrogen-containing austenitic stainless steel bar sequentially includes smelting, electroslag remelting, and forging. During electroslag remelting, the steel ingot obtained in the smelting process is used as an electrode bar of the electroslag furnace and is remelted with specific slag and crystallized. The specific slag comprises CaF2 (65-70%), Al2O3 (15-20%), CaO (5-10%) and MgO (2-5%) in percentage by weight. Specific forging methods, including upsetting-and-drawing and radial forging, are used. In upsetting-and-drawing, the pass deformation is less than 35%, the pass reduction is 50-80 mm, the pass heating temperature is 1130-1150° C., and the pass deformation method is ellipse-ellipse-circle. The method can obtain the low-carbon high-strength nitrogen-containing austenitic stainless steel with uniformly distributed chemical composition, high purity and high strength.