The complex working conditions of the field were analysed, and the roll body was divided into roll neck, roll end, roll shoulder, rolling area and non-rolling area. The influence factors, such as the segmented cooling, the back-up roll, the friction heat and the deformation heat and etc. were synthetically considered, and the boundary conditions that agree with the practice were constructed, then a mathematical model of work roll temperature field was established based on thermal equilibrium principles. Through the experiments completed in the Bao Steel 1580 hot mill, the transient variation and the variations before and after each strip rolled of the thermal camber were analysed in detail, and the reasons for the discontinuity of thermal camber were accurately analysed. The calculation values coincide better with the measured ones, and good effects are obtained. It indicates that the model has better engineering practicability, and provides important basis for on-line prediction and control of the roll thermal deformation.