Nowadays, Nickel-containing stainless steel plays more important role due to its good mechanical properties including superior bending strength and hardness. Meanwhile, the phosphorus content of Ni-Fe alloys needs strict requirements when it is treated as the base material of stainless steel. Oxidizing dephosphorization and reductive dephosphorization (RDP) are two methods for dephosphorization of ferroalloys. However, the conventional oxidizing dephosphorization process is not a good choice for dephosphorization of High Silicon Ferronickel because silicon or other valuable metals will be oxidized in priority of phosphorous in the practical production. In this case, RDP has been noticed because of its protection of silicon and valuable metals as well as its excellent dephosphorization effect. Even though, there are still some problems which need to be solved. Like the reaction product of calcium phosphide (Ca3P2), is very active and produces the hazardous phosphine gas (PH3) when it is exposed to the moist atmosphere which will pollute the environment and need to be treated to be environmental friendly. What is more serious, PH3 is also very dangerous to human being. A small amount of inhalation can cause dizziness, headaches, sickness and vomiting. Severe PH3 poisoning can cause damage to lungs, heart, liver and kidney, and even cause death. Therefore, it is very important to dispose the reaction product of Ca3P2, and suppress the evolution of PH3. Then the RDP slag can be stacked safely or used as raw material for other products. In the present study, the authors wish to exploit different kinds of oxidative metallurgical slags to oxidize the RDP slag, in order to make Ca3P2 transform into calcium phosphate (Ca3(PO3)2) which is innocuous. This work aimed at reviewing studies on the treatment of reductive dephosphorization slags reported by several authors. The results showed that ferromanganese slag which contains MnO could be successfully used to treat Ca3P2 innocuously.