Large-size autostereoscopic 3D LED displays are commonly used in outdoor or large indoor space, and have the properties of long viewing distance and relatively low light intensity at the viewing distance. The instruments used to measure the characteristics (crosstalk, inconsistency, chromatic dispersion, etc.) of the displays should have long working distance and high sensitivity. In this paper, we propose a methodology for characteristics measurement based on a distribution photometer with a working distance of 5.76m and the illumination sensitivity of 0.001 mlx. A display panel holder is fabricated and attached on the turning stage of the distribution photometer. Specific test images are loaded on the display separately, and the luminance data at the distance of 5.76m to the panel are measured. Then the data are transformed into the light intensity at the optimum viewing distance. According to definitions of the characteristics of the 3D displays, the crosstalk, inconsistency, chromatic dispersion could be calculated. The test results and analysis of the characteristics of an autostereoscopic 3D LED display are proposed.