The invention discloses a pre-reducing type manganese series desulfurizing agent which mainly comprises the following raw materials in percentage by mass: 30-85 percent of an active manganese oxide, 0-40 percent of a metallic oxide and 12.7-30 percent of an accessory ingredient, wherein the metallic oxide is one or several of an active ferric oxide, an active copper oxide and an active zinc oxide; the accessory ingredient consists of the following components in percentage by mass: 93.3-96.7 percent of a mineral additive and 3.3-6.7 percent of sodium carboxymethylcellulose; the mineral additive is one or several of high-aluminum powder, kaolin and bentonite. Furthermore, the invention also discloses a preparation method for the pre-reducing type manganese series desulfurizing agent. The pre-reducing type manganese series desulfurizing agent disclosed by the invention is applied to an industrial device, so that the device operating time can be greatly shortened, and the operating cost can be lowered; meanwhile, an accident of temperature runaway caused by a large amount of released heat during reduction of the manganese series desulfurizing agent can be avoided.