The present application discloses a binder for a lithium ion battery, which comprises a polymer obtained through emulsion polymerization of a monomer in the presence of a reactive emulsifying agent. The binder is used in fabrication of a lithium ion electrode plate, whereby a thin film formed on the surface of an electrode membrane and fine channels formed in the electrode membrane with the use of a conventional emulsifying agent during the electrode membrane-forming process are eliminated, and the lithium ion conductivity of the electrode membrane is improved. Meanwhile, with the use of the reactive emulsifying agent, the bonding effect of the binder and the stability of the electrode membrane are improved, thereby greatly improving the charging rate and cycle life of the lithium ion battery.