Abstract: The difference on the surface potential of the cracks generated in different stress state was studied by comparative analyzing on the surface potential of wing crack and secondary crack in the uniaxial loading test of the granite plate with 45° pre-existing crack.The results showed that when the role of secondary crack appears as a broken belt,the surface potential of secondary crack which generated by compression is more complex than wing crack which generated by tension.When the role of secondary crack also appears as a single crack,the surface potential of the two cracks generated in different stress state do not have significant differences on the changing trend.The complexity of the surface potential of the crack extending is not directly correlating with the stress state which generates the crack,but with the crack pattern.