The performance of gas turbine has relation with the environmental temperature and in hot weather its output is reduced with the increase of air inlet temperature,which can be solved by means of cooling the inlet air.An designing method of the gas turbine inlet air cooling system has been proposed,an inlet air cooling system of the gas turbine with two operating conditions has been presented,and the development of the monitoring system,which is designed by WinCC and STEP7 was introduced.The operation results show that the said inlet air cooling system to have obvious economic fits.