The laminar cooling of hot slabs is a distributed-parameter system characterized by time varying, nonlinear factors and physical difficulties in continuous temperature measurement. The process operation is classified into operating points according to steel No., thickness and target temperature. The moving slab is divided into segments upon which the control is to be implemented. The technology of soft sensing is incorporated into the temperature prediction model of the process that is adapted online to find the through-thickness temperature distribution, which will be used for online error correction in closed-loop control. Industrial experiments have shown the effectiveness of the proposed method.