Principal component analysis of Landsat data obtained over the estuary area of the Haihe River-Yongdingxin River in the northwest of the Bohai Bay shows the different pollution gradations of the sea water. Principal component transformation of the organic pollution data measured in situ was also performed. The values of the first principal component were divided into three regions to show the different pollution gradations at these experimental sites. The results of the investigation show that the geographical distribution of the different pollution gradations obtained from remotely sensed data agrees with that from sea-truth measured data.