Systematically monitoring the baseline sensitivity of troublesome weeds to herbicides is crucial for the early detection of a premature market lifespan of herbicides. Florpyrauxifen-benzyl is one of the most important rice herbicides across the world, which has been used for five years in China. Barnyardgrass is one of the main targeted weed species of florpyrauxifen-benzyl. Totally 114 barnyardgrass populations were collected from rice fields in Jiangsu Province, China, and screened for susceptibility of each population to florpyrauxifen-benzyl by whole-plant bioassays. For all populations, the GR50 doses (the dose causing a 50% reduction in fresh weight of aboveground parts) of florpyrauxifen-benzyl ranged from 1.0 to 34.5 g ai ha-1, with an average of 6.8 g ai ha-1, a baseline sensitivity dose of 3.3 g ai ha-1, and a baseline sensitivity index of 34.5. Twenty-one days after treatment with florpyrauxifen-benzyl at the labeled dose (36 g ai ha-1), 90% of the barnyardgrass populations showed reductions in fresh weight of aboveground parts > 95%. Compared with the baseline sensitivity dose, 63, 44, and seven populations had no resistance (55%), low resistance (39%), and moderate resistance (6%) to florpyrauxifen-benzyl, respectively. Furthermore, the GR50 distribution of barnyardgrass populations did not show a significant correlation with city, planting methods (direct-seeding or transplanting), and rice species (ssp. indica or ssp. japonica) at the seed-collection rice fields (P > 0.05). In conclusion, florpyrauxifen-benzyl remains effective for barnyardgrass control in rice fields despite serious resistance challenges.