Aiming at the fact that with the increasing output energy of oxygen-iodine chemical lasers in China, one of the main factors limiting the quality of the beam is the misalignment of the optical cavity during the light emission process, a method for self-collimation of optical resonators based on image processing was proposed. This research method uses helium-neon light to pass through the central hole of the concave cavity mirror, and an industrial camera is placed behind the convex cavity mirror to form an interference concentric ring above the screen. Through the image processing methods such as binarization and Hoff circle detection in the OpenCV library, the center coordinates of the interference concentric ring are obtained, and the image is divided into four parts: upper, lower, left, and right. The difference of the number of bright pixels between these four parts is used to estimate the offset state of the interference concentric ring, and then the theoretical criterion for the change of the optical resonator under the cavity condition is obtained. The experimental results show that this method can obtain quite accurate optical resonance cavity misalignment criterion. The misalignment criterion is selected from the difference between the left and right bright pixels of 30 000, and the difference between the upper and lower bright pixels of 45 000.