Abstract: The rolling theory deals with only simple rolling condition, but in fact, any rolling procees has, more or lees, some nonsymmetry For instance the diameters between two worle rolls are not absolutely equal This papes diecribes the experience on a four-high strip mill The tests proved that even a little difference between two xork rolls in diameters may cause unequal distribution of the rolling torque. This ought to be the foundation of strength computation of driving pavts. Under certain conditions, cold strip mill may use "single-roll drive and unequal diameter rolling" The practice proved that it could bring us three advantages:increase in reduction, decrease of the rolling pass and the saefty of driving parts.