Abstract:The comparative studies on the spectral characteristics of the chlorophyll-protein complex CPa isolated separately from spinach chloroplast preparation, O2-evolving PSⅡ preparation and PSⅡ reaction center core complex showed that the CPa band isolated from the former two preparations contained not only Chl a but also small amount of Chl b. This is different from the general view that there is only Chl a but no Chl b in CPa band. Furthermore, the Chl b content in CPa from the chloroplast preparation was higher than that of O2-evolving PSII preparation. It was found that there was only one chlorophyll-protein complex band, i.e., CPa band in PSⅡ reaction center core complex. So it is considered that PSⅡ reaction center chlorophyll-protein complex must be included in CPa band; but at least in the chloroplast preparation and the O2-evolving PSII preparation, some other components were also contained in CPa.