The diet of Common Kestrels Falco tinnunculus was studied during the breeding seasons from 2004 to 2008 in Northeast China. Diet was determined by direct observation of the prey brought to nests, and analysis of prey remains collected from nests. Fifteen vertebrate species from three classes, and two groups of insects were identified as prey items. Rodents were the main prey items, comprising 93.9% of the total prey items （TPI） and 97.0% of total prey biomass （TPB）. Birds, frogs and insects were also eaten. The kestrels preferred to prey on small rodents （mean weight 20-40 g） and displayed density-dependent prey selection. Daily prey consumption of an adult and a nestling was 2.6 individual rodents or 87.6 g, and 1.7 individual vertebrates or 48.2 g, respectively. The estimated prey consumption of a breeding pair （adults and nestlings） during the breeding season was 520.1 individual vertebrates or 19.7 kg.