In recent years, repeated red tides have caused great damage to the coastal areas of China. As a much more important manner for red tide monitoring than any other remote sensing method, Pushbroom Hyperspectral Imager (PHI) can obtain abundant high resolution and continuous hyperspectral data. In this paper, through the analysis of the hyperspectral data acquired above the North China Sea by airplane from June to August of 2001, the methods for detecting and identifying red tide water are discussed on the basis of creating the fault color image, extracting the reflectance curve of the abnormal district and constructing the correlative function.