Abstract: Based on the measured data of water bodies collected on april 23^rd, 24^th, June 1^st and July 6^th, 2016 and the GOCI (Geostationary Ocean Color Imager) satellite remote sensing images of the same period, the Chl a concentration in Qinhuangdao sea area is studied. The NDPI (normalized dark pixel index) method is used to analyze the correlation between the radiance and Chl a concentration of eight band combinations of the images. The band combinations with correlation coefficient≥70% are selected as independent variables to construct the Chl a concentration inversion model (R²=0.956). The average relative error of the model is 25.3% verified by independent phase measured data. The Chl a concentration in Qinhuangdao sea area from December 2017 to November 2018 was retrieved by using this model. The results show that the concentration of Chl a in the coastal area of Qinhuangdao is generally higher, the overall concentration in autumn and winter is lower, and the peak concentration appears in summer.