A method for measuring the étendue of LED was proposed based on the near-field model of the LED source. The curve of luminous power on étendue can be obtained by tracing rays data in LED near-field moled, which can directly reflect the étendue characteristics and the energy efficieny of LED source. Taking the UV-LED array surface source in the exposure system as an example, the actual measurement of the three different models of UV-LED were carried out. The designer can make a judgment on the UV-LED beam quality by the étendue and energy efficiency curve, which can provide help for the optimization design of the UV-LED array surface source.