The invention discloses an automatic plate rolling device and method for a corrugated carton printing machine. According to the device, a gear frame is arranged on a roller shaft of a printing roller,a first plate rolling gear and a second plate rolling gear are arranged on the gear frame in parallel, a telescopic rack is meshed with or separated from the first plate rolling gear under the driveof an air cylinder, the second plate rolling gear is connected with a plate hanging shaft gear through a plate hanging gear, the plate hanging shaft gear is arranged at one end of a plate hanging shaft, and the plate hanging shaft is arranged inside the printing roller in a parallel manner. The method comprises the following steps of driving the telescopic rack to be meshed with or separated fromthe first plate rolling gear through a cylinder; during meshing, the plate hanging gear rotates around the second plate rolling gear to drive the plate hanging shaft gear to rotate, so that an offsetplate is driven by the plate hanging shaft to be screwed tightly; and during separating, the printing roller can be used to carry out printing. By controlling the extension and contraction of the telescopic rack, the working principle of a plate hanging gear system can be changed, so as to realize automatic plate mounting. The automatic plate rolling device has the advantages of being convenient to operate and capable of effectively preventing human errors and improving the printing precision.