Abstract: The strength and fracture mechanism analysis of conducting polythiophene thin film is carried out by means of electronic speckle pattern interferometry(ESPI)and SEM observation. The film was synthesised by a typical electrochemical method. Experimental results show that the effect of thickness on the fracture mechanism of conducting polythiophene thin films is significant and the initial microstructure of the thin film plays an important role. In particular, there are many defects on the free surface when the thickness is greater than 10~15mm. The defects mainly consist of bigger molecular granules, a porous microstructure and microcracks caused by released residual stress. The effects of the thin film thickness on fracture model, microcracks caused by residual stress. are discussed based on many SEM profiles. It is shown that the initial microstructures of the thin film under the electrochemical synthesis condition can affect the mechanical properties of the polythiophene thin film.