Though high accuracy of the thermal contour was obtained while adopting finite element method, it could not meet the real-time requirement. One-dimensional finite difference method could realize real-time control in the case of neglecting both the circumferential and radical heat exchange, but the over-simplified modes resulted in poor accuracy. And two-dimensional full explicit difference was also limited in practical application since its time step was restricted to keep the model stable. Consequently, a new method of alternating direction finite difference was introduced and discussed in the models stability, calculating speed and precision. Specific work roll after one real rolling unit was researched, The result shows that error of temperature on work roll surface between measured and calculated values is within 5 ℃. The influence of rolling rhythm and strip width on thermal crown was also studied. The conclusion is verified theoretically and practically that it can maintain absolutely stable and meet the online requirement.