The eccentricity of the optical axis of the large-aperture concave ellipsoid mirror will cause the misalignment of the optical system of the remote sensing camera, resulting in the deviation of the imaging focal plane from the designed position. To solve this problem, an aspheric system based on optical flat compensation was designed according to the geometrical parameters of the mirror. Through sensitivity analysis and calculation, it was found that the optical flat misalignment 1" had no effect on the system aberration. The primary mirror misalignment 1″ caused a coma of 0.04λ (λ=632.8 nm). Combined with the results of simulation calculation, the test optical path was built, and the eccentricity of the mirror was measured by theodolite and laser tracker. The error analysis shows that the tilt error of the primary mirror is about 1.2″, and the eccentricity measurement error of the primary mirror is 0.028 mm, which can meet the measurement requirements of the large-aperture mirrors of most space remote sensing cameras.