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Check dams have been widely used in China's Loess Plateau region due to their effectiveness in erosion and flood control. However, the safety and stability of the check dam decrease with the operation process, which increases the probability of dam failure during flood events and threatens local residents' life and property. Thus, this study simulated flood process of the check dam failure in the Wangmaogou watershed in Yulin City, Shaanxi Province, China, calculated different types of inundation losses based on the flood inundation area within the watershed, and determined the number of key flood protection check dams by classifying the flood risk levels of the check dams. The results showed that 5 dams in the watershed were subject to overtopping during different rainfall return periods, which was related to their flood discharge capacity. Dam failure flood process showed a rapid growth trend followed by slow decrease, and the time of flood peak advanced with increase in the return period. After harmonization of evaluation scales, the magnitude of flood inundation losses can be ranked as: economic losses (212.409 million yuan) > life losses (10.368 million yuan) >ecological losses (6.433 million yuan). The risk value for both individual dams and the whole dam system decreases as the return period increases. The number of key flood protection check dams in the Wangmaogou watershed was 2, 3, 3, 3, 4, and 5 for floods with return periods of 10, 20, 30, 50, 100, and 200 years, respectively. The results provided a theoretical basis for the safe operation and risk evaluation of check dams in the Loess Plateau Hills watershed. [ABSTRACT FROM AUTHOR]