Photodamage of some pigments in the isolated photosystem Ⅱ (PS Ⅱ) reaction center D1/D2/Cyt b559 complex from spinach has been investigated by means of high performance liquid chromatography. The light induced damage of pheophytin a (pheo a) in the complex was observed for the first time. The content of pheo a decreased about 47% by illumination, suggesting only one of the two pheo a molecules in the PSⅡ reaction center complex was damaged. No damage of β carotene was found.