Abstract: In order to improve the effect of automatic detection of isolation switch's closing state, a non-contact automatic detection method based on laser displacement sensor was adopted. The resolution of the laser displacement sensor was maximized, the optical parameters of the laser displacement sensor was optimized, and its displacement measurement accuracy was improved; Through the laser displacement sensor with optimized optical parameters, the isolation switch contour curve was collected, and the isolation switch contour curve sampling point set was obtained. Using the least square method, the elliptic equation of the sampling point of the isolation switch contour curve was fitted, and the angle between the conductive arm and the horizontal direction was calculated. When the angle of the conductive arm was within the specified interval, the reasonable switch closing was determined to be in place, and the non-contact automatic detection of the isolation switch closing state was completed. The experimental results show that the angle of the front and back conductive arms calculated by this method is about 0.4° and 0.5° respectively, which is lower than the specified interval of the angle. The results indicate that this result is helpful to realize the non-contact automatic detection of the isolation switch.