The diet of Long-eared Owl (Asio otus) was studied by checking pellets collected in Urumqi City, Xinjiang Uygur Autonomous Region, China. Total of 1 132 prey items were identified from 683 pellets in 3 winters of 2009 to 2011. Six small mammals and two species of bird were preyed. By checking the frequency of each food composition in pellet samples, we found that small mammals were the main food items, Mus musculus constituted 53.45% of the food items and was the most common species of prey. Small mammals accounted for 88.16% of food composition and contributed 95.13% biomass of in pellets. There were significant differences in the prey composition among years. It indicated that the difference of food items and predation rate of prey species were related to the availability of prey resources in the habitat and Long-eared Owls was an opportunism predator.