The invention discloses a device for automatic steel wire spool feeding, constant-tension wire unwinding and automatic shutdown during wire break. The device is characterized in that a driving disc and a brake disc are arranged at the two ends of a main shaft seat and are installed on a machine frame, a first brake and a second brake are arranged on the two sides of the brake disc, a duplex oil-water separator is arranged above the brake disc, the main shaft seat, a continuous rotary jacking air cylinder, a pulley, a button and a hand-turn valve are arranged on the machine frame, and a wire passing wheel and a limit switch are arranged on a swing arm. A spool is pushed to the pulley, a left centre and a right centre are aligned with a taper hole of the spool, the hand-turn valve is operated to enable the continuous rotary jacking air cylinder to push the spool, the pulley slides to enable the left centre and the right centre to be jacked into a spool hole, the continuous rotary jackingair cylinder jacks the spool through the thrust, a steel wire enters a wire drawing machine box body after being wound around the wire passing wheel on a wire passing arm, the friction force of the first brake on the brake disc is adjusted to control the tension of the steel wire, when the steel wire is broken, a wire passing roller strikes the limit button, and the wire break signal is transmitted to an electromagnetic reversing valve to enable the second brake to brake. According to the method and the device, the operation rate is high, and the labor intensity is reduced.