NOVELTY - Synthesis of benzidine derivative comprises: (i) coupling aniline derivative, ferric chloride or its hexahydrate oxidizer and solvent in a reactor; and heating to 40-200 degrees C; continuing stirring for 1-10 hours to obtain reaction solution of the benzidine derivative; (ii) naturally cooling the reaction solution; adding saturated potassium carbonate solution or aqueous ammonia for completely stopping the reaction; extracting; combining the extracted liquid, washing; drying; filtering; evaporating and concentrating the filtrate; purification; and draining to obtain pure product.    USE - The benzidine derivatives are useful in the dye industry for producing direct dye, acidic dye, reductive dye, ice dye, sulfide dye, active dye and organic dye.    ADVANTAGE - The process is simple, easy to operate, energy conserving, has low production cost, environmentally friendly, has convenient application, yields benzidine varied derivative with high output rate, good quality and suitable for industrial production. The product has high electrical conductivity, applicable to light-emitting diode, field-effect tube, organic optical conductor component and organic solar battery thus satisfying the wide range and large requirements in the market.    DETAILED DESCRIPTION - Synthesis of benzidine derivative by one step oxidization and coupling of aniline derivative comprises:    (i) using aniline derivative as a raw material, ferric chloride or ferric chloride hexahydrate as oxidizer; coupling aniline derivative, ferric chloride or its hexahydrate and solvent in ratio of 1:(1-10.5):(1-10.5) by first adding the ferric chloride or its hexahydrate and the solvent into a reactor, adding the aniline derivative under an agitation; and then heating to 40-200 degrees C; continuing stirring for 1-10 hours to obtain reaction solution of the benzidine derivative, where the solvent is toluene, dichloromethane, tetrahydrofuran, ethyl acetate, acetonitrile, ethanol or dimethylsulfoxide;    (ii) concentrating and product purifying comprising naturally cooling the reaction solution of the benzidine derivative in air; adding saturated potassium carbonate solution or aqueous ammonia for completely stopping the reaction; using dichloromethane for extracting until no benzidine derivative exists in extracted liquid detected by thin layer chromatography; combining the extracted liquid, washing with water and saturated salt solution; drying using anhydrous magnesium sulfate; filtering; rotatably evaporating and concentrating the filtrate; processing chromatograph purification by silica gel column; eluting; rotatably evaporating and concentrating the liquid from the silica gel column; and draining to obtain pure product, where the eluent is mixed solution of the ethyl acetate and petroleum ether in volume ratio of 1:(70-100).