Abstract: Banded structure of S355J2W steel plate for EMU parts was evaluated by image recognition technology. The microstructure image of the sample was obtained from the microscope by the camera. The image was processed by digital image processing method, and then the feature objects were extracted and counted. Finally, the evaluation result was calculated. The results show that the relative accuracy of banded structure evaluation of S355J2W steel plate was less than 30%, which met the requirements of banded structure evaluation standard. The influence of subjective factors were reduced and the work efficiency was improved by the image recognition technology.