This study presents an effective three-dimension (3D) motion measurement system for civil infra-structures. The proposed system consists of hardware (three camcorders, one commercial PC, and one frame grabber) and software. The efficient software and measurement scheme, and automatic optimal threshold selection algorithm are successfully developed to obtain the dynamic motion with six degrees of freedom in real-time. The images of target panels attached to a structure are captured by three camcorders and then streamed into the PC via the frame grabber. Then six degrees of freedom of the dynamic motion are calculated using image processing techniques with pre-measured calibration parameters. Several laboratory tests including static and dynamic tests were conducted to verify the effectiveness of the proposed system with an error of less than 4%.