Tapioca starch was used as the main material and self-developed organic-bentonite used as the modifier to make tapioca starch/bentonite composite binder by melting and solution intercalation technologies.The binder was characterized by means of FTIR,XRD and mechanical performance test.The results showed that the interlamellar spacing of improved organic bentonite was larger than that of organic bentonite and Na-bentonite,and the more the interlayer spacing of bentonite,the more advantageous the binder to the intercalation reaction between starch and bentonite,leading to higher dry tensile strength.The nanometer composite binder also features high bond strength,good humidity resistance,low costs and simple process,and is environment-friendly.