A poly（6-thioguanine-co-o-aminobenzene sulfonic acid）（P6-TG-ABSA） film modified glassy carbon electrode（GCE）（P6-TG-ABSA/GCE） was fabricated by electrochemical copolymerization of 6-thioguanine（TG） and o-aminobenzene sulfonic acid（ABSA）.The surface morphology and electrochemical activity of the modified electrode were investigated by scanning electron microscopy（SEM） and electrochemical methods.The SEM images show that the copolymer film exhibits a granular surface structure with regular and homogeneous particles，which is helpful to the electro-catalytic oxidation of the analytes.The results of cyclic voltammetry（CV） and differential pulse voltammetry（DPV） show that the modified electrode exhibits strong electro-catalytic activities toward the oxidation of ascorbic acid（AA） and dopamine（DA） in 0.1mol?L-1 phosphate buffer solution（PBS，pH 5.0）.Compared with those at P6-TG/GCE and PABSA/GCE，the current responses in anodic peak signal remarkably increase and the peak potential separation is 0.20V at P6-TG-ABSA/GCE，which could be used for the simultaneous determination of AA and DA mixture with high sensitivity.Under the optimum conditions，the linear dependences of DPV current responses for AA and DA are observed in the concentration ranges of 2-5000μmol?L-1 and 2-180μmol?L-1,with correlation coefficients of 0.9998 and 0.9997，respectively.The detection limits（S/N=3） of AA and DA are 0.06μmol?L-1 and 0.05 μmol?L-1,respectively.The different electrochemical behaviors of AA and DA at P6-TG-ABSA/GCE at various scan rates indicate that the electrode reaction of AA is a diffusion-controlled process,and that of DA is an adsorption-controlled process.The P6-TG-ABSA/GCE is applied in the simultaneous determination of AA and DA concentrations in human urine samples with satisfactory results.