This paper suggested a process that high nickel (Ni > 25%) alloy was produced by laterite ores smelting reduction in the condition of high oxygen level. In order to find the slag type used for this process, the metallurgical properties of FeO-SiO2-CaO-MgO slag system were studied by consulting the slag phase diagram, thermodynamic calculation and laboratory experiments. The results showed the slag, contained CaO 20-23 wt%, FeO 15-15 wt%, MgO 19-21 wt%, SiO2 38-42 wt%, has lower melting temperature range (1543-1573 K) and suitable viscosity. The smelting experiment indicated that the recovery ratio of Ni was more than 95%, and the content of NiO in the slag can be decreased to less than 0.15%. This will create a new way to utilize laterite ores.