Electrocatalytic oxidation of hydrazine (HZ) was studied on an stable modified glassy carbon electrode (GCE) based on poly (4-aminobenzene sulfonic acid) (4-ABSA) film. The 4-ABSA-modified glassy carbon electrode was prepared by electrochemical polymerization technique in phosphate buffer solution (PBS) (pH 7.0) and its electrochemical behavior were studied by cyclic voltammetry (CV). The polymer filmmodified electrode has very high catalytic ability for electrooxidation of HZ, which appeared as a reduced overpotential in a wide operational pH range of 5-10. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 1.31 x 10(-7) and 4.35 x 10(-7) M for CV; 7.89 x 10(-8) and 2.63 x 10(-7) M for CA, respectively. The results of experiments showed that prepared modified electrode have good stability, sensitivity and reproducibility for at least one month if stored dry in air.