At present, molten blast furnace slag is quenched rapidly using a large amount of water to produce a glassy-granulated slag without any recovery of its much sensible heat, polluting water and atmosphere. To solve these problems, a new heat recovery system is proposed. This system consists of melting gasifier, the 2nd gasifier and boiler in order to achieve stepped energy using. The melting gasifier and the 2nd gasifier use the endothermic heat of gasification reaction instead of sensible heat to recover the energy of molten blast furnace slag. The possibility of the new heat recovery system is studied. The reactions in melting gasifier are studied using STA409PC thermal analyzer and HSC chemistry software. The economic and environmental benefits are calculated based on the heat and mass balances. The results indicate that this method is possible and better than conventional methods such as hot water or steam production. The molten BF slag acts as not only thermal media but also good catalyst. The efficiency of melting gasifier is high and without pollution. Besides, this method can bring huge economic and environmental benefits which are important to the survival and sustainable development of iron-steel enterprises.