Abstract: Based on the Gas Steam combined cycle power plant (CCPP) of Baosteel power plant, a detailed analysis of the performance of CCPP under off design conditions is carried out. In order to improve the traditional modeling methods which are based on mechanism of focusing on the performance under design conditions and having the difficulty to improve the precision of models when the unit is far away from the design conditions, a hybrid mode which combines the mechanism model based on the performance curves with the data derived model based on KPLS is established. The inputs of the hybrid model are ambient temperature/pressure, fuel flow, cooling water temperature/flow and steam turbine back pressure and the output of the bybrid model is the net equipment output. KPLS which is integration of PLS and kernel function can deal with the nonlinearities. The data derived model based on KPLS with high accuracy is used to correct the error of the mechanism model which has clear physical meaning. Based on the history data of the CCPP of Baosteel power plant, the performance of the hybrid mode is compared with that of the mechanism model. Experiments indicate that the precision of the hybrid mode is higher than that of the mechanism model.