The invention provides a method for monitoring the two-dimensional displacement and the strain of a structure based on the digital image processing technology. The method is characterized in that a circular pattern is adopted as a target, wherein the target is a shooting object used for being shot to acquire a digital image, the displacement or the strain of a corresponding point, to be monitored, of the structure can be determined by processing the digital image, the circular pattern guarantees the non-directional feature of the cross section of the target, namely, the target does not need to be strictly adjusted to be right during monitoring of physical quantities of the structure, in common words, the situation that due to inclination of the target, the circular pattern becomes rhombic from being square like a square pattern is avoided, and the circular pattern can be kept circular all the time; a square pattern with the known side length is adopted as a calibration plate, wherein the calibration plate is a shooting object for calibration of a current vision monitoring system; a circular circle center is selected as the feature of the image of the target to be extracted, wherein the feature is a monitoring calculation point selected for determining the corresponding displacement or strain of the structure from the shot digital image of the target.