Monocular visual measurement suffers from a lack of depth information, making it difficult to accurately calculate the three-dimensional deformation of cracks. To address this issue, this paper proposes a three-dimensional crack measurement method that integrates multiple coordinate systems. By designing a concentric circle array target and establishing an equivalent displacement model for cracks, the problem of measuring the three-dimensional deformation of cracks is transformed into the problem of measuring the three-dimensional deformation of the main and auxiliary plates of the target. By taking photos with a camera, density clustering and eccentricity correction are performed on the images to obtain a set of feature points. Then, the EPnP algorithm is used to obtain the projection matrix, and the least squares method is used to reconstruct the sub panel point set in three dimensions. The coordinates of the sub panel point set in a given world coordinate system are obtained, and the change in the front and rear coordinates of the sub panel, that is, the three-dimensional deformation value of the crack, is calculated. The accuracy, robustness, and generalization ability of the proposed method were verified through three-axis sliding table tests. The results showed that the algorithm had a maximum deviation of 0.35 mm under indoor conditions, and the measurement errors in all three directions were within ±0.35 mm, can still maintain a measurement accuracy of ±0.4 mm under on-site test conditions，meeting the requirements of crack measurement standards (±0.5 mm).