Abstract: Light emitting diode (LED) has been the most popular lighting source around the world for its varieties of advantages such as energy-saving, environmental friendly, seismic and longeval. LED luminaries are usually assembled by aligned packaged LED dies, which are surface sources. In order to measure the light distribution accurately, the detector should be placed far enough away from the luminary. The measurement distance is called far-field distance which makes the surface source be considered as the point source. There are a variety of national standards defining the value of far-field distance; however, the defined distances are different from each other and only the impacts of the maximum source size are considered. In this study, the far-field distance of LED array luminary was investigated. The farfield distance of lamps with different intensity distributions, LED array sizes, LED array arrangement densities and LED array arrangement styles were calculated first. Then, the impacts of these parameters on far-field distance were analyzed. Finally, suggests to determine the far-field distance of LED array luminaries were given. This research could offer reference for the accurate measurement of the far-field distance intensity distribution of LED array luminary.