Abstract: Since the establishment of Liaohe Conservation Area in 2010, its governance and protection has changed from multi-department water control, section-by-section management and segmentation of trap and block to overall planning, centralized management and comprehensive protection. Based on the comparative analysis of water quality monitoring data of 8 sections in Liaohe main stream from 2006 to 2019, the temporal and spatial distribution characteristics and influencing factors of water quality and main pollutants before and after the establishment of Liaohe Conservation Area were discussed. The results indicated that the water quality of the main stream of Liaohe River had been greatly improved ever since designation of the protection zone, and the water quality inferior to Class Ⅴ of Environmental Quality Standards for Surface Water(GB 3838-2002)had been completely eliminated. The concentrations of COD and NH₃-N decreased significantly, and the water quality of the whole Liaohe River remained at Class Ⅲ-Ⅳ, although they fluctuated in 2018. In terms of spatial distribution, the water quality in the upper reaches of the reserve (Tieling section) was the worst, the middle reaches (Shenyang section) was slightly better, and the lower reaches (Anshan and Panjin sections) became worse. From upstream to downstream, the concentrations of main pollutants COD and NH₃-N increased firstly, then decreased and then increased. The effective implementation of water pollution control and water environment management of "three major projects" and "three campaigns" in Liaohe Conservation Area had played an important role in improving the water quality. The agricultural non-point source pollution in the upstream and the discharge of domestic sewage and industrial sewage in the downstream were the main factors for the spatial difference of water quality and pollutants in Liaohe Conservation Area.