Palaeodiet is one of the most important topics in modern archaeological research. The bulk isotopic analysis of archaeological human and faunal remains have made great contributions in palaeodietary reconstruction for decades, but gradually it shows the limits of palaeodietary interpretation, of particular, in the way to detect the nutritional quality and food pattern of ancient human. Compound-specific amino acid composition method (CSIA) has shown huge potential to elucidating dietary behaviors in a complex archaeological context and may able to mitigate the influences of many of the limitations inherent to palaeodietary reconstructions. Here we carried out both bulk collagen isotope analysis and the compound-specific amino acid isotope analysis on 10 humans and 4 faunal skeletons which excavated from a Vandalic cemetery at Carthage in Tunisia, North Africa (5th—6th AD). The result reveals that the population from Vandal Cemetery had an overall dietary pattern that was predominately based on terrestrial C₃ resources, and the majority of the individuals having a significant amount of terrestrial protein in their diets. Further, this study focuses on determining the difference in the contribution of protein to the human diet and comparing the interpretation variance given by these two different methods. The individual amino acid isotope result shows the great advances in trophic position estimation for both archaeological human and animal’s samples. It may shed new light on the exploring identity dietary difference and the social stratification research in Chinese archaeological research. Our studies indicated that the CSIA has a huge potential for refining human paleodietary reconstruction, and should be widely applied into Chinese Archaeology.