Abstract: Combined cycle is currently an important technology for natural gas power generation. Further improving efficiency is the demand for the development of combined cycle. By using the quasi-1D turbine cooling model and the concise estimation model of thermodynamic performance for bottom cycle, on the basis of the key parameters which represent the "cooling-material" technology (H-class), the present work performed the influence of parameter variation of gas turbine on cooling air and efficiency of combined cycle. The effects of main parameters such as component efficiency, the "cooling-material" technology, combustor exit temperature and pressure ratio on the performance of the system were obtained. The results show that, under H-class "cooling-material" technology level, the performance improvement of combined cycle brought by increasing the combustor exit temperature and pressure ratio is small. Even when combustor exit temperature is 2000℃, the optimal efficiency of combined cycle is only 2 percentage points higher than that of 9HA.02 gas turbine combined cycle. To further increase the efficiency of combined cycle, it is necessary to comprehensively improve the component efficiency and "cooling-material" technology level. Results may provide references to improve the efficiency of combined cycle.