Abstract: Studies on the structure of chlorophyll-protein complexes of algal PSI and the characteristics of their long-wavelength fluorescence are reviewed, and comparied with those of higher plants. The diversity of algal PSI forms a sharp contrast with the identity of PSI of higher plants, and has the characteristics of phylumla. Comparitive studies between the. PSI of algae and higher plants will contribute a better under standing to the structure, function and evolution of PSI.