The invention belongs to the technical field of battery materials and particularly relates to a flame-retardant additive for electrolyte and flame-retardant lithium ion battery electrolyte. The flame-retardant additive provided by the invention is at least one of the following compounds and the structural general formula of the flame-retardant additive is as shown in (I), wherein R is any one of alkyl, alkoxy, halogenated alkyl, halogenated alkoxy, halogenated alkylene, phenyl, xenyl, halogenated phenyl, halogenated biphenyl, alkyl silicone, alkoxy silane, alkyl phosphate, alkoxy boron and acylamino; and halogen is F, Cl or Br, and the halogenation is partial or full substitution. Electrolyte using the flame-retardant additive has low viscosity, low toxicity, wide electrochemical window and temperature range and has a high flame retardant effect at the same time; a lithium battery using the electrolyte not only has good electrochemical performance, and the security is improved greatly, so that the lithium battery has a wider application market.