The invention relates to a bi-benzene-sulfonate interface initiator and a preparing method thereof. A tertiary amine compound with bi-benzene-sulfonate anions and bi-dodecyl is synthesized, and the characteristics of a surfactant are shown; meanwhile, tertiary amine and potassium peroxodisulfate can be subjected to a redox reaction at the normal temperature, cation free radicals are formed on nitrogen atoms and then converted into carbon free radicals at adjacent positions, generating of the free radicals can be repeated, control is flexible, multi-phase concatenation polymerization is achieved, polymerization of styrene and butyl acrylate and polymerization of styrene and N,N-dimethyl acrylamide are sequentially triggered on a water/oil interface, and a multi-segmented copolymer is obtained. An experiment proves that the feeding ratio of monomer and the composition ratio of the copolymer are quite coincident, it shows that the triggering efficiency of the initiator is high, the polymerization reaction in the mode is moderate and controllable in condition and low in energy consumption, other organic solvents and emulsifiers are avoided, the product is pure, and the requirements of green chemistry are completely met.