The invention discloses a steelmaking residual heat step recycling method. The invention belongs to the technical field of steel industry iron-making residual heat and residual energy utilization. The method is adopted under a condition for further utilizing iron-making low-grade residual heat, and comprises step recycling and high-efficiency utilizations of blast furnace gas residual heat, dust removal air residual heat, water slag residual heat, hot air furnace low-temperature flue gas waste heat, and dust cover and slag ditch residual heat. According to the technical scheme, blast furnace gas residual heat and dust removal air residual heat obtained after furnace top residual pressure power generation are connected in parallel, and are supplied for domestic water, cooling, or heating. Recycled water slag residual heat and flue gas residual heat obtained after hot air furnace gas heat exchanger are connected in parallel, and are used for supplying a heat source for low-temperature seawater desalination. Recycled dust cover residual heat and slag ditch surface radiation heat are connected in parallel, and are supplied for blast furnace gas supplementary firing residual heat boiler power generation. After powder generation, high-temperature seawater desalination is realized by a steam method. Cooling water and domestic water are treated and are adopted as inlet water replenishment. Through step recycling and graded utilization of the low-grade residual heat and residual energy, steel system comprehensive energy consumption can be reduced to a maximal extent, and energy resource reasonable utilization and comprehensive optimized utilization can be realized.