An online iron alloy baking furnace used in a converter belongs to the technical field of converter steel making and is used for baking and preheating alloy materials of the converter steel making. The technical scheme includes that the online iron alloy baking furnace comprises a furnace frame, a furnace body, a combustor and a furnace cover. The furnace body is fixed on the furnace frame, the furnace frame and the furnace body are installed on a middle vacant area between the position under an alloy weigh hopper and the position above an alloy rotary chute, the combustor is arranged on the upper portion of the furnace body, the furnace cover is arranged on the upper portion of the furnace body, a discharging pipe passes through a flap valve under the weigh hopper to be directly inserted into the furnace cover, the furnace cover is further provided with a dedusting pipe, the lower portion of the furnace body is provided with a quadrant valve, and the lower portion of the quadrant valve exactly faces the alloy rotary chute. The vacant space above the rotary chute at the back of the converter is innovatively utilized, and the problem that off-line baking of the converter occupies large area and investment is large is resolved. Single furnace alloy materials are utilized in the baking, baking effect can be easy to achieve in a short time, and the equipment is simple and good in dedusting effect. The lifting furnace cover resolves the safety problem that a closed baking furnace is prone to explosion.