For energy saving and consumption reduction,the waste heat recovery of flue gas from sinter straight cooler is very important to steel enterprises.The close flow system of waste heat recovery of flue gas cools the sinter using the exhaust from the boiler of waste heat recovery,which can elevate the temperature of recovery flue gas to make the best use of waste heat,and to reduce environment pollution enormously.For elevating the temperature and the ratio of waste heat recovery,the principles of the waste heat recovery cycle system of flue gas were discussed.Numerical model of energy equation of the cycle sysytem was built,the flue gas flow of cycle and the optimal selection of flue gas were also carried out.The design program of the cycle system of flue gas were also carried out.The theory and technology of the recovery waste heat are provided to the great energy consumption enterprises.