The process of a detection method of printed lines width based on flatbed scanner was proposed as follows: the reflection coefficient calibration card was designed, the reflection coefficient was calibrated,the algorithm and calculation progamm on MATLAB was prepared according to the line width definition in ISO 13660,and then measure the line width was measured in detecting figure with scanner and print quality inspection system. Through test data analysis the effectiveness and applicability of the method were confirmed.It is concluded that the method can be used for printing line width detection, and the accuracy of the method and stability of the detection process are also fine.