The invention belongs to the technical field of displacement measurement and relates to an automatic three-dimensional displacement monitoring method for arch dam deformation. The method comprises the steps of dividing an arch dam into n sections, measuring a three-dimensional displacement value at the position of an end point of a first section, and monitoring the three-dimensional variation of the end point of each section, relative to the previous end point, so as to obtain the three-dimensional displacement value of the end points of all the sections according to a transfer principle. The method is simple and feasible, and convenient for engineering implementation, conforms to the practical engineering monitoring needs, provides an effective means for automatic three-dimensional displacement monitoring on the arch dam and overcomes the defect that the original measurement method only can monitor one-dimensional or two-dimensional displacement; in addition, the practical deformation condition of a dam body is combined, while the measurement effectiveness and the measurement precision are ensured, the corner parameter monitoring on a platform part of a measured part is cancelled, the measurement process is optimized, the measurement device is simplified, the measurement reliability is improved and the measurement cost is reduced.