Abstract: The goal of this work was to investigate the antidepressant fraction from Radix Paeoniae Alba and identify its major chemical constituents. Corticosterone injured rat phaeochromocytoma (PC12) cells and behavioral despair depression models of mice were used to evaluate the antidepressant effects of Radix Paeoniae Alba (Bai-Shao) ethanol extract (BS-E) and its three fractions (BS-10E, BS-60E, BS-95E) isolated by macroporous resin column chromatography. Animal experimental procedures were approved by the Animal Ethics Committee of the Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences and Peking Union Medical College (approval No.: SLXD-20210618051). The results showed that BS-E, BS-10E and BS-60E had protective effects against PC12 cells injury induced by corticosterone, among which BS-60E had the strongest protective effect. BS-60E could significantly shorten the time of forced swimming and tail suspension in despair depression models of mice, and was identified as the antidepressant fraction of Radix Paeoniae Alba. The major chemical constituents in the antidepressant fraction were identified by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS), and their proposed fragmentation pathways in MS spectra were deduced. A total of 79 chemical constituents were identified from BS-60E, including 36 monoterpenes, 34 polyphenols, 6 oligosaccharides, and 3 other constituents, and monoterpenes and polyphenols may be major effective constituents of BS-60E.