Barnyardgrass ( L.) is the most serious weed threatening rice production, and its effects are aggravated by resistance to the quinclorac herbicide in the Chinese rice fields. This study conducted a comparative proteomic characterization of the quinclorac-treated and non-treated resistant and susceptible using isobaric tags for relative and absolute quantification (iTRAQ). The results indicated that the quinclorac-resistant had weaker photosynthesis and a weaker capacity to mitigate abiotic stress, which suggested its lower environmental adaptability. Quinclorac treatment significantly increased the number and expression of the photosynthesis-related proteins in the resistant and elevated its photosynthetic parameters, indicating a higher photosynthetic rate compared to those of the susceptible . The improved adaptability of the resistant to quinclorac stress could be attributed to the observed up-regulated expression of eight herbicide resistance-related proteins and the down-regulation of two proteins associated with abscisic acid biosynthesis. In addition, high photosynthetic parameters and low glutathione thiotransferase (GST) activity were observed in the quinclorac-resistant compared with the susceptible biotype, which was consistent with the proteomic sequencing results. Overall, this study demonstrated that the resistant enhanced its adaptability to quinclorac by improving the photosynthetic efficiency and GST activity.