Based on the experimental model of the two-span continuous beam,through the collection of video of vibration of the continuous beam,and by using the method of converting the video into digital image,the polynomial fitting method is used as the calculation method of the sub-pixel precision image edge recognition from the image edge detection technology to detect the sub-pixel edge for each picture,and obtain the position of the edge of the beam at each moment.Through acquiring the data of the entire beam edg...