According to the objective measurement indexes of digital printed line quality defined in ISO 13660 standard, the measuring method of each main quality indicator was analyzed. On the one hand, the required 600 dpi measuring image was obtained by scanner on the basis of the rules in ISO 13660 standard. Then the indicators such as line width, raggedness, blurriness and so on were analyzed and calculated by means of Hough transform, edge tracing, and lines fitting. On the other hand, the relationship between gray value and density value was established through function fitting, which made the calculation of opacity in ISO 13660 standard come true. At last, the algorithm was tested through selecting five samples. Experimental results showed that the algorithm can better realize the measurement and calculation of each line quality indicator.