Abstract: For safety evaluation of insulators in power system, a nondestructive testing method based on the random vibration response analysis is proposed. The vibration modes and random vibration response of insulator are investigated in Finite Element software of Abaqus. According to the actual fracture location of the pillar ceramic insulator, the upper and lower flange, the numerical simulation and experimental tests are conducted on insulators with cracks. It is shown that the offset of resonant frequency in random vibration response can be used as indicator for the nondestructive evaluation of insulator. If there are cracks in upper flange, the resonant frequency will shift to higher frequency; if there are cracks in lower flange, the resonant frequency will shift to lower frequency. Moreover, the influence of crack depth on the shift of resonant frequency is investigated.