To improve the measuring precision of photoelectronic measurement system for curvature (important status parameter of cannon), a real-time distortion correction method with concentric circles as onsite standard is proposed and a set of measuring apparatus with self-center adaptation is designed. Firstly, the eccentric distortion is corrected by adjusting the horizontal and vertical location of target in the measuring apparatus. Then, the distortion situation of optical system is detected in real time based on the concentric circles as onsite standard which is extracted by using curvature estimation. Finally, the correction is made for the curvature measuring result to accomplish it with high accuracy according to the detection. Experiment results show that the method proposed is quite stable, fast and accurate. Compared with the traditional correction methods, the measuring errors of curvature measuring system whose focus is 6.00 mm are improved from±0.15 mm to±0.05 mm after correction, and the time of a single correction is less than 0.49 s, which can improve the measuring precision of system efficiently.