Abstract: The evaluation methods of inclusions in steel were introduced. The evaluation methods of inclusion width, length and OG type inclusions in DIN 50602—1985 standard were analyzed. The results show that the inclusion area was used to evaluate the inclusion grade in DIN 50602—1985 standard, which could highlight the influence of inclusions on the properties of steel. For the super-long single string inclusions, the overall length and width of the inclusions to grade the inclusions was recommended, without segmentation and additional dimensioning. According to the figure 1 of DIN 50602—1985 standard, the area of inclusions was calculated, and then the area of inclusions was calculated according to the table 3 in the standard. It was concluded that the evaluation boundary values of OG type inclusions were basically the same, so the grade of inclusions could be evaluated according to the diameter of OG type inclusions.