The invention relates to a method for controlling full automatic roll changing of a hog finishing mill. Hardware used by the method consists of a controller, a 
server, an operating computer and a roll changing 
bogie, wherein the 
server and the operating computer are connected with the controller respectively, and the controller controls operation of the roll changing 
bogie. The control method comprises the following steps in sequence: preparation of roll changing, disassembly of the prior working roll, 
assembly of a novel working roll, and preparation of steel rolling, wherein jacked 
pile position value E7 of the roll changing 
bogie on an upper working roll realizes relative 
position control by a self-adapting positioning method; the position value E7 is calculated by 
contact position value E9 of the roll changing bogie and a finishing 
machine frame minus 420 millimeters; and the 
contact position value E9 of the roll changing bogie and the finishing 
machine frame is obtained by judgment of the absolute position of the roll changing bogie before the finishing 
machine frame, the reference velocity, the actual velocity and the working current of a motor; and after automatic roll changing is subjected to manual interference, automatic roll changing is continuously completed by utilizing the 
breakpoint continuing function of an SFC module of programmed 
software P80i in the controller, and quick full 
automation of the roll changing process is realized.