As one of the most important centres of origin for the genus Citrus L., China is rich in wild mandarin germplasm. In this study, phenolic compounds in the peels of 14 wild mandarin genotypes native to China were determined and their antioxidant capacities were evaluated using DPPH, FRAP, ABTS and ORAC methods. We found that Nieduyeju had the highest total phenol content (51.14mg/gDW), and Wulongsuanju had the highest total flavonoid content (20.66mg/gDW). Hesperidin, the dominant flavonoid, was observed to be highest in Guangxihongpisuanju (55.98mg/gDW). Ferulic acid was the most abundant phenolic acid analyzed, and Nieduyeju (7780.17μg/g DW) and Guangxihongpisuanju (13,607.19μg/gDW) had the highest contents of extractable and bound phenolic acid, respectively. Antioxidant potency composite (APC) index showed obvious variations ranging from 58.84 to 98.89 in the studied wild mandarins, among them, Nieduyeju had the highest APC index. Overall, Guangxihongpisuanju, Nieduyeju, Cupigoushigan and Daoxianyeju contained more phenolics and exhibited higher antioxidant capacities than the mandarin cultivars Satsuma and Ponkan.