The invention discloses a method for manufacturing steel cylinders. The method sequentially includes a tube cutting procedure, bottom forming, bottom scraping, gas tight testing for a bottom, necking-in for a steel cylinder, polishing, notching, drilling, heat treatment, external shot blasting, threading, internal shot blasting, flaw detection testing, other external shot blasting, paint spraying, drying, winding, solidifying, volume testing, valve mounting, gas tight testing and finished product packaging. A spraying quenching device comprises a quenching water tank, at least two sliding oblique plates, at least two rotating rollers, a spraying chamber, a lifting device for lifting a front door of the spraying chamber, another lifting device for lifting a rear door of the spraying chamber, a spraying main water pipe and at least one spraying pipe, the sliding oblique plates are arranged above the quenching water tank, the rotating rollers are rotationally disposed above the quenching water tank, each rotating roller is positioned between the corresponding two adjacent sliding oblique plates, the spraying chamber is arranged above the sliding oblique plates, the quenching water tank is communicated with the spraying chamber, a spraying quenching hollow chamber is formed between the quenching water tank and the spraying chamber, the spraying main water pipe is arranged in the spraying quenching hollow chamber, and the spraying pipes are arranged on the spraying water main pipe.