Synthetic slag suitable for unpolluted deoxidization with voltage applied between metal and slag

The invention relates to synthetic slag being applicable to extra electric field pollution-free deoxidation between slag and metal and belongs to the field of the metallurgy of iron and steel refinement technical skill. The synthetic slag is characterized in that the synthetic slag has the following compositions by weight percent: 40-55 percent of CaO, 40-55 percent of Al2O3, 1-10 percent of MgO, 0.01-1 percent of FeO, and 0-1 percent of MnO; and CaO/ Al2O3 is equal to 0.8-1.2. The synthetic slag is characterized by low melting point, rapid melting speed, good fluidity, few volatilization, high oxygen ionic conductivity and the like. In addition, no dust pollution happens in the using process, premelting slag component is closer to the existing refining slag component, and few reformations are carried out to the prior art so that the cost is low.