The invention discloses a general acquisition method for a weak contrast collimation image target center of a comprehensive diagnosis system, which adopts a unified method to acquire optical target centers of different types of images, and is simpler and more practical compared with the existing method. The method mainly comprises the following steps: 1, constructing an original image into a multi-dimensional image cube; 2, performing dimension reduction processing on the multi-dimensional image cube to obtain a first-dimensional image after dimension reduction; 3, performing K-means classification on the first-dimensional image after dimension reduction to obtain a binary image; 4, judging whether the binarized image is a schlieren small ball image or not, and if so, obtaining a schlierensmall ball target separation image; if the image is a pinhole image, feature points on the circular contour of the pinhole image needing to be obtained; if the image is another image, directly acquiring a target center of the image by using a gravity center method; and 5, carrying out circle fitting on the pinhole image and the schlieren small ball image by using a least square method to calculate the circle center of the images so as to obtain the center of the optical target.