The invention relates to a method for treating copper slag by a rotary hearth furnace. The method comprises the steps of raw material treatment, burdening, mixing, forming, material drying, roasting reduction, flue gas treatment, finished product cooling, ore grinding, magnetic separation and iron powder cold pressing, and adopts a hydrocarbon combined reduction technology to reduce iron oxide into metal iron, reduce zinc oxide into metal zinc, volatilize, oxidize and collect, so that Fe2SiO4 in the copper slag can be efficiently reduced, the metallization rate of direct reduction iron of an intermediate product can reach 90% or above, the zinc removal rate reaches 95% or above, and the iron recovery rate of the whole process reaches 85% or above; the hydrocarbon combined reduction technology is adopted, the reduction temperature is low, and the energy consumption is low. according to the process, the reduction temperature is 800-1230 DEG C; hydrogen is adopted as a main reducing agent in the later stage of reduction, a by-product is water, green and environment-friendly effects are achieved, and the carbon emission amount of treated copper slag per ton is 50-70% of that of a carbon metallurgy rotary hearth furnace process; and the reduction coal in the process is low-rank coal instead of anthracite, so that the cost is low.