The invention relates to steel for a flux-cored wire jacket and a manufacturing method thereof. The steel solves the problem that the existing steel has bad component matching degree with the flux core, more impurity element content, low elongation percentage and low welding wire deposited metal obdurability, and easily produces strip breakage, and the like. The measure is as follows: the steel comprises chemical constituents according to the weight percentage: 0.012-0.038% of C, 0.003-0.009% of Si, 0.20-0.29% of Mn, 0.015-0.05% of Cu, 0.015-0.19% of Al, 0.001-0.005% of Re, less than or equal to 0.01% of P, less than or equal to 0.008% of S, less than or equal of 0.002% of N, the rest of Fe and unavoidable impurities. The manufacturing method is as follows: carrying out melting procedures such as hot metal desulfurization, converter blowing, RH vacuum treatment and the like on steel ball components which are continuously cast and form a briquette; and then carrying out hot rolling and reeling; and finally pickling, cold rolling a single rack, cover annealing, finishing, oiling and packaging. The steel has low carbon, silicon and phosphorus, low yield ratio, high purity, good ductility and component matching with the flux-core.