The invention provides a rotary furnace cooling agent and a manufacturing method thereof. The cooling agent is a carbonic and ferreous conglomeration which mainly takes iron scale, carbonic dry ash and ferreous dry waste material as raw materials, and prepared by additionally adding caking agent into the raw materials. The weight percentage of the main chemical compositions of the cooling agent meets the following condition: the carbon content is 5-25%, the content of TFe is more than or equal to 50%, the content of S is less than or equal to 0.50% and the content of P is less than or equal to0.50%. The manufacturing method comprises: the iron scale, the carbonic dry ash and the ferreous dry waste material are firstly sent into a blending machine to be mixed together and evenly mixed withthe caking agent; after being evenly mixed, the materials are sent into a mixing mill and then into a twin-roller ball press machine to be pressed into conglomeration; the pressed conglomeration is screened by a sieving machine, and the qualified screened conglomeration can be sent into a dry furnace to be dried, so that the finished product conglomeration can be obtained. The rotary furnace cooling agent can be used for replacing the common waste steel to be applied in smelting of a rotary furnace; compared with the prior art, the cooling agent completely uses the waste materials generated in the steel production, so that the process flow is short, the cost is low, the using method is flexible, the adding quantity is large, the recovery rate is high, the field operation is seldom affected, the economic benefit and the environmental protection benefit are remarkable, and the promotion and application values are excellent.