Rock fall is a common geo-disaster that threatens people’s properties and lives in Taiwan. For the sake of train safety, a rock fall protection fence, named ultra-light fence, was built along a slope where a railway track is passing by. Sensors with on-board gyroscope and accelerometer were installed and placed on the posts of the fence to record the tilt angle of the rock fall protection fence. The data were analyzed and uploaded to Internet in real time, and applied in websites and Apps. When the data reaches the threshold, alarm signals will be sent out in terms of light, sound, and text message, etc.