Methylene methane disulfonate(MMDS) has been used as an additive in lithium ion battery electrolyte in recent years because of its unique ring structure. At present, the research on it is still in the initial stage in China. The synthetic  method of by combining inorganic and organic chemical reactions was determined by reference. Fitdy the important raw material of the target product,silver methylane disulfonic acid, was synthesized by using sodium methylene disulfonate as raw material through a simple three-step  inorganic reaction of barium salt conversion, sulphuric acid acidification and silver salt conversion, then it reacted with diiodomethane to get synthesizing product. The synthetic method has the advantages of simple process, safe operation, solvent recycling, cost saving and pollution reduction. The purily of MMDS is higther,and the total yield is 57.9%, higher than the reported value.