Abstract: To improve the safety of Li-ion battery, the specific flame-retardant electrolytes and their properties were studied. Triphenyl phosphate(TPP) and dimethyl methyl phosphonate (DMMP) were used as the cosolvent in 1M LiPF6/EC:DEC (1:1 in weight) to reformulate the nonflammable electrolyte. The flame-retarded ability, thermal and electrochemical performances with these electrolytes were studied. The results show that the optimal mass fractions are 55% TPP and 35% DMMP by controlling the flame-retardant efficiency (η≥0.9) of the electrolytes. Furthermore, the modified electrolyte matches the electrode materials well in both physical and electrochemical stability.