The invention relates to a production technology of sponge iron for a water purifying agent. The production technology comprises steps as follows: (1), a dried and finely ground iron-containing raw material is mixed uniformly with a carbonaceous material, a pore-forming auxiliary and binder components, and a mixture is pressed into balls; (2), green balls are dried and mixed uniformly with a reducing agent and a desulfurizing agent, preheating, reducing and cooling are performed in a coal shaft furnace, and a sponge iron mixture is obtained; (3), after the sponge iron mixture is subjected to magnetic separating, sponge iron metallized pellets and residual coal are obtained; sponge iron particles obtained after crushing and screening of the sponge iron metallized pellets are used as the water purifying agent. The production technology has the remarkable advantages of being advanced, reliable, stable in product quality, low in production cost, high in production efficiency and environmentally friendly, and large-scale production can be realized; the produced sponge iron water purifying agent has the advantages of large specific surface area, high specific surface energy, higher electrochemical enrichment, physical absorption and flocculation precipitation and the like, and can be widely used for treating various kinds of wastewater with difficulty in biochemical degradation.