In this study, a curvature change tracking program was developed to evaluate curvature changes in the main reflector of a very long baseline interferometry (VLBI) antenna structure. The data from the geometric model that was developed by fitting the main reflector into a three-dimensional (3D) ellipsoid model were used as the fundamental data for the tracking program. The 3D ellipsoid fitting model was established using the 3D position coordinates of the feature points on the reflector surface extracted through nontarget-based close-range photogrammetry. To enhance the fitting accuracy of the 3D ellipsoid model, the optimal parameters were calculated by minimizing the residuals between the conjugate points and the ellipsoid fitting model and by removing outliers. As a result, it was statistically confirmed that the fitting accuracy of the ellipsoid model was improved. The improved ellipsoid model was incorporated into the curvature change tracking program. The developed program will be used to evaluate the structural stability of the main reflector based on periodic curvature calculations, which can also be used as fundamental data for repair and reinforcement work in the future.