A blue poly(azure B) film has been synthesized using repeated potential cycling between -0.25 and 1. 10 V (versusSCE). The electrolytic solution consisted of 2.5 mmol dm~(-3) azure B, 0.5 mol dm~(-3) NaCl and 0.2 mol dm~(-3) NaH_2PO_4 at the pHrange of 2.0 to 11.0. The in situ visible spectrum during electrolysis of azure B shows that the intensity at 740 nm peakincreases with increasing numbers of potential cycles, which is attributable to the formation of poly(azure B). Thewavelength of its corresponding absorption peak is 98 nm longer than that of azure B. The polymerization rate is stronglyaffected by pH values. The anodic peak potential and cathodic peak potential of the poly(azure B) in a solution of pH 3.0 arenot affected by increasing the scan rate from 25 to 600 mV s~(-1). Poly(azure B) has good electrochemical reversibility and fastcharge transfer characteristic in the pH range of 2.0 and 11.0. The conductivity of poly(azure B) is 1.5×10~(-4) S cm~(-1).According to the differences between FTIR spectra of poly(azure B) and azure B, an electrochemical polymerizationmechanism of azure B is proposed in this paper. A blue poly (azure B) film has been synthesized using repeated potential cycling between -0.25 and 1.10 V (versus SCE). The electrolytic solution consisted of 2.5 mmol dm -3 azure B, 0.5 mol dm -3 ) NaCl and 0.2 mol dm ~ (-3) NaH 2 PO 4 at the pHrange of 2.0 to 11.0. The in situ visible spectrum during electrolysis of azure B shows that the intensity at 740 nm peak incitions with increasing numbers of potential cycles, which is attributable to the formation of poly (azure B). Thewavelength of its corresponding absorption peak is 98 nm longer than that of azure B. The anodic peak potential and cathodic peak potential of the poly (azure B) in a solution of pH 3.0 arenot affected by increasing scan rate from 25 to 600 mV s -1. (azure B) has good electrochemical reversibility and fast charge transfer characteristic in the pH range of 2.0 and 11.0. The conductivity of poly azure B) is 1.5 × 10 -4 S cm -1. According to the diffe rences between FTIR spectra of poly (azure B) and azure B, an electrochemical polymerization mechanism of azure B is proposed in this paper.