Monitoring water environmental quality of large rivers is the basis of river evaluation and local environmental protection worldwide. This study compared the water quality of the Rhine and the Yangtze River, two of the world’s most important arteries, based on monitoring data collected from their monitor stations from 2007 to 2018. Dissolved oxygen (DO), pH, chemical oxygen demand (COD)/dissolved organic carbon (DOC) and ammonia-nitrogen (NH₃-N) were used to evaluate their water quality. The changing trend, the temporal and special patterns were also analyzed. It was found that the overall water quality of the Rhine in the last decade (p = 0.95) was better than the Yangtze (p = 1.01). Notably, COD_Mn and NH₃-N were identified as main pollution factors of the Rhine and the Yangtze, respectively. This study provided information for water quality modelling, therefore might be helpful for the water quality management of China.