In the comparison and selection of high-sensitivity detectors, the sensitivity, imaging contrast and resolution are important indicators to evaluate the imaging capability. The standard test method of resolution has a high demand for the environment and complicated and inconvenient. In this paper, we introduce a low-light-level resolution testing and comparing system to facilitate and compare and evaluate the sensitivity, imaging contrast and resolution of different high-sensitivity detectors, and provide the basis for the selection of the detector. The pattern of the target plate is designed. The target plate is made of an optically chrome-plated plate and the inner wall of the enclosed system where the optical system is located is coated with a black diffuse paint to reduce the interference of the stray light to the test. According to the sampling theorem, in order to ensure that the narrowest stripes after imaging meet the resolution testing requirements of the detector which has the smallest pixel, the narrowest stripe width of the imaging on the photosensitive surface should be less than 1/2 of the smallest pixel. The use of focusing makes it can still be clearly imaged when there is a small assembly error, but the focusing should not affect the test results. Finally, the system is used in an experiment, testing and comparing the resolution and sensitivity of three detectors, and verify the effectiveness and convenience of the system.