The invention discloses a high-efficiency compound desulfurizing agent, relating to the ladle desulphurization accessory field. In the existing ladle desulphurization, the uniserial desulfurizing agent is uniformly adopted, with narrower function, and non-agreeable desulphurization effect. Aiming at the condition that small and medium-sized steel mills do not have liquid iron pretreatment systemsor desulphurization stations, and do not have powder spraying desulphurization devices, the desulfurizing agent of the invention adopts ingredient with multi-components, namely, the compound desulfurizing agent consisting of limestone, calcined soda, fluorite, calcium carbide, magnesium powder and caustic-calcined magnesite, with the weight proportion of 40 to 50, 10 to 20, 5 to 15, 10 to 20, 4 to6 and 5 to 15 sequentially. The desulfurizing agent has the following advantages that: 1. the integral desulphurization capability is strong, and the sulfur content can be reduced to 20ppm; 2. sulfursubstance can be contained, and resulfurization phenomenon can not be generated; 3. the desulfurizing agent can be directly poured, and equipment and investment are not needed to be increased; and 4.the desulphurization speed is high.