Abstract: The study of water environment pollution is an important means to control watershed pollution.Taking the Minjiang River basin as an example,the trend of water quality change at 16 monitoring stations in the study area from 2004 to 2020 was analyzed by using the Seasonal Kendall Trend Analysis method,and the main pollution identification and analysis of 13 monitoring points from 2017 to 2020 were conducted by using the Time Series Global Principal Component Analysis method.The results showed that the pH and DO of tributaries were higher than those of the main stream,the main stream was lower in the upper and middle reaches and higher in the lower reaches,COD and NH₃-N decreased first and then increased in the main stream from the upper reaches to the lower reaches,TP increased first and then decreased.In addition,Kendall's test showed an improving trend in pH and DO in the study area,while TP and NH₃-N were at higher risk of contamination and some sites needed more attention to COD.Finally,Time Series Global Principal Component Analysis was used to identify that the current water pollution pressure in the study area mainly comes from NH₃-N and TP,especially the pollution control of tributaries in the basin needed to be strengthened.