Abstract: The classification and internal relations of the three types of internal stresses were systematically described. It is pointed out that in addition to the well-known residual stresses in the industry, the microscopic stress, especially the second type of internal stress, also has important engineering application value. A possible method-the focused ion beam (FIB) minimally invasive method for measuring the second type of internal stress was given. Finally, the effects of the three types of internal stresses on the fatigue properties of the materials were analyzed and elaborated in detail.