The Loess Plateau witnessed accelerated social complexity during the Longshan Culture period. The emergence of human sacrifice like the Lushanmao Site not only reflects the regional characteristics of social evolution but also becomes a key window to decode local social stratification. Nevertheless, little is known about dietary differences among people of different social statuses, especially between tomb owners and human sacrifice. Here we focus on the human sacrifice tombs at the Xiaoyingpanliang locality and related remains at the Majiawa locality of the Lushanmao Site. By applying AMS-14C dating, multi-isotope (S13C, S15N) analysis of human bone collagen, tooth enamel, and dentin serials, it systematically explores the correlation between the dietary structure of the population and their social identities. The S13Ccol values and dentin serials show a lifelong C4 diet (crops being foxtail millet and common millet) with weaning completed by around age three. Minimal differences between rib-limb bones indicate stable diets and sedentary lifestyles before death. There was a significant difference in S15N values among different individuals, particularly the highest S15N value and the lowest Delta 13Cap-col of the occupant of M1, which implies that this individual has consistently consumed high-protein foods since childhood. In contrast, the S15N values of human sacrifices are generally low, forming a clear dietary distinction. The discovery of human sacrifice at Xiaoyingpanliang represents the earliest practice in northern Shaanxi (4410-4080 cal. a BP). Collectively, these findings offer key isotopic and archaeological evidence for understanding social complexity on the Loess Plateau in the late Neolithic.