Suspended on Mg-base melt, SrCl2 was electrochemical reduced to prepare Mg-Sr alloy. The kinds of Sr-compounds, composition ratio of flux, temperature of molten salt and Mg-base molten bath and recovery of Sr were discussed. According to theories and experiments, this paper presents the relations between the adding flux and reduction of Sr-compounds with the technical parameters. The electrode reactions and the Gibbs Free Energies were evaluated based on thermodynamics analysis. The results show that composition of flux played important roles in the reduction process. The optimized technical flow and parameters for the application of the new method were advised.