A small part rotation center-adjusting method based on image auxiliary belongs to the field of precision measurement and machining. The small part rotation center-adjusting method depends on image auxiliary equipment to achieve various ultra-precision machining and detect non-contact damage-free center adjusting of a part installed on the equipment. Small parts with centers to be adjusted are installed on a two-dimensional displacement center-adjusting platform face, a computer system captures an image a, and gyration centre coordinate of the small parts with the centers to be adjusted is supposed to be (xc and yc); the position coordinate of an excircle center is obtained to be (x1 and y1) and is identified on the image a; a rotation main shaft rotates for a known angle theta and then a new image b is captured; a new position coordinate (x2 and y2) on the new image b and the excircle outline radius are determined; the gyration centre coordinate (xc and yc) of the small parts with the centers to be adjusted is calculated; and positions of the excircle center coordinate (x3 and y3) and the gyration centre coordinate (xc and yc) of the small parts with the centers to be adjusted on a dynamic image c are coincided. The small part rotation center-adjusting method is suitable to rotation center adjusting of small parts easy to damage and deform.