GIS is one of most important power devices in power systems. However, much research focused on the partial discharge rather than the mechanical fault. In this paper, mechanical fault detection based on vibration signals were used. Firstly, vibration signals were collected on the surface of GIS equipment. Then vibration images were generated from the vibration signal sequences. A vibration images CNN (VI-CNN) mechanical fault detection model was used in this paper based on the vibration images. Finally, the VI-CNN model performed well during the test. The performance reveals that the method can be used in GIS monitoring system to detect the mechanical state of GIS.