Background: Synchrotron radiation is a special light produced by synchrotron radiation facility

and has been widely used in many fields because of its properties of broad spectrum

high brilliance and excellent collimation. The beam spot size is one important feature of the beamline. The current method used for measuring the spot size is scanning knife-edge technique

which is accurate but time consuming. Purpose: The aim is to find an effective method to get the spot sizes more quickly and more intuitively based on the image processing. Methods: Basic image processing method and adaptive threshold binarization method are employed to resolve the problem. Results: The results show that the image processing program can get the spot size correctly

although the spot size varies in a large range

and what’s more

the new method can show the information about the spot center and spot symmetry simultaneously. Conclusion: The new method is faster and more intuitive compared with the others currently used and it can be considered as an effective diagnosis tool during beamline operation. Abstract