Objective:To investigate the anti-inflammatory effects of water extract of the Iris halophila root on lipopolysaccharide（LPS） stimulated RAW264.7 cells and analyze its chemical constituents. Method:The supernatant of YWG prepared by water extraction and alcohol precipitation was separated by AB-8 macroporous adsorption resin column chromatography to obtain ethanol eluates with different concentrations （YWG，YWG-0%，YWG-20%，YWG-40%，and YWG-60%）. Cell counting kit-8（CCK-8） assay was used to determine the effects of YWG-0%，YWG-20%，YWG-40%，and YWG-60% on the viability of RAW264.7 cells. Griess assay was employed to detect the nitric oxide （NO） level in LPS-stimulated RAW264.7 cells. The release of tumor necrosis factor（TNF）-α，interleukin（IL）-6，IL-10，and IL-1β was detected by enzyme-linked immunosorbent assay（ELISA）. YWG and the elution site with the most robust anti-inflammatory activity were identified and compared by ultra-high performance liquid chromatography-quadrupole-time of flight-mass spectrometry （UHPLC-Q-TOF-MS/MS）. Result:Ethanol eluates with different concentrations inhibited the release of NO，TNF-α，IL-1β， and IL-6 in the supernatant of LPS induced RAW264.7 cells （P<0.05），and promoted the release of IL-10 （P<0.05）. YWG-60% displayed a highly significant effect （P<0.01）. A total of 127 constituents were detected from the comparison of YWG and YWG-60% by UHPLC-Q-TOF-MS/MS in the positive and negative ion modes，including 61 flavonoids. YWG-60% contained 25 flavonoids with elevated content as compared with YWG. Conclusion:YWG-60% showed potent anti-inflammatory effect，and the effective anti-inflammatory constituents were presumedly flavonoids. The findings of this study are expected to provide a scientific theoretical basis for the basic research on the medicinal effect of the water extract of YWG.