Abstract: The status of post insulators is related to the safety of power plants and substations.For post insulators have their own characteristics, the on-line detection of defects in post insulators via acoustic vibration method has both theoretical and practical basis, by analyzing the vibration spectrum of the post insulator, the status of the insulator could be evaluated.By combining acoustic vibration method with wireless transmission system, more efficient testing of post insulators could be achieved, hence avoiding the negation of defects sprouted between two adjacent detection periods, and misjudgment caused by environmental factors or human error.The fatal accidents of electric power system can be reduced by using this method, thus the safety of the grid is guaranted.