Reduction kinetics of stainless steel slag in iron bath smelting reduction was studied at the temperature of 1500°C ~ 1650°C. It was concluded that the reduction process consisted of two parts. That is to say smelting reduction was controlled by stainless steel slag melting initially and by interface reaction later. In order to increase smelting reaction rate, the melting point of slag should be decreased at the first stage and adjust the liquidity of slag at later stage. Smelting reaction rate will be accelerated by means of optimize the slag content. The optimal reduction result that all most all of the chromium in slag been recovered was obtained in temperature was 1500°C, basicity of slag was 1.0~1.2, the value of Al2O3+MgO was 25%.