In response to the shortcomings of insufficient consideration of ecological service benefits in current evaluation of irrigation water use efficiency at irrigated oasis scale in arid regions, a new indicator and method to evaluate irrigation water use efficiency considering ecological water consumption were proposed and applied in irrigated oasis of the Yellow River in Ningxia Hui Autonomous Region. The results show that the average proportion of irrigation water in farnland evapotranspiration consumption is 74.7%, and that in ecosystem evapotranspiration consumption is 39.8%. Irrigation water plays a significant role in supporting the ecosystem. The difference between irrigation water use efficiency with and without considering ecological water consumption is 0.052~0.074, accounting for 13.9%~16.1% of the irrigation water efficiency without considering the ecological water consumption, and the ecological service benefit of irrigation water is obvious. The proposed indicator and method are reasonable and feasible, and can objectively reflect the comprehensive benefits of irrigation water use.