The melting point and viscosity of SrO SiO 2 CaO Al 2O 3(5%) Na 2O(10%) CaF 2(10%) flux system have been measured,and the curve charts of the melting point and viscosity are drawn.Moreover,the mathematical relations of properties with chemical composition are founded.The best range of chemical composition for mould flux containing SrO is presented via analyzing the curve charts.