Abstract: The artificial blind hole defect samples were tested by using fluorescent penetrants with different system sensitivities, and the differences in the display results of artificial blind hole defects by using fluorescent penetrants with different system sensitivities were analyzed and verified. The results show that the sensitivity of the post-emulsification penetrant is higher than that of the water washable penetrant when the fluorescent penetrants with the same system sensitivity are used to detect the artificial blind hole. For holes, the relation between their diameter and depth is an important factor affecting the sensitivity of penetrant testing.