Modulation transfer function (MTF) is one of the important parameters for the image quality evaluation of optical satellite cameras. On-orbit MTF estimation has a bearing on the application of remote sensing data and the future development of remote sensing cameras. For the photoelectric imaging system widely used for earth observation at present, according to the physical definition of MTF, the satellite cameras are subjected to on-orbit MTF estimation through subpixel position detection and parameterized model fitting, during which the special point, line, and plane targets for convenient mathematical description are taken as references, such as reflecting point source arrays, radial targets, and large-area knife-edge targets. The experimental results show that the point source method is the most rigorous estimation approach and can fully characterize the imaging capability of remote sensing cameras. In contrast, with the assist of large-area targets, the square wave method can directly obtain the MTF value at the Nyquist frequency of the imaging system, and the knife-edge method is a common estimation method of optical cameras but can only have access to the MTF in the orbit direction and that perpendicular to the orbit direction. On-orbit MTF values obtained by the above three methods are of good consistency and the maximum relative error is smaller than 6.00%. At the same time, the above methods have their own characteristics and varied applicability.