Abstract: The influence function is used to analyze the influences of workpiece width, rolling force, sizes of work/back-up rolls and bending force acting on roll on the crown of loaded rolls of a conventional 4-high plate mill. With lots of data regressed in calculation, an on-line computation model is given for loaded roll crown. Then, the genetic effect of workpiece crown at entry of rolling process on that at exit is discussed, and an on-line prediction model of plate crown is thus given integrating the model of loaded roll crown with that of plate crown's genetic coefficient. The model can predict actually the crown magnitude of rolled plate with high precision because the effect of lateral plastic flow of workpiece in rolling process has been taken into account. So, it is efficient to on-line control of plate shape especially its crown.