Abstract: PS Ⅱ reaction center D1/D2/Cyt b-559 purified from chloroplasts of spinach has four components of fluorescence decaying with lifetimes of 1.0 ns, 5.9 ns,24 ns,and 73 ns whose fractions to total fluorescence yield are 0. 05,0.34,0. 35 and 0.26 respectively. The fluorescence emission spectra of these lifetime components are closely overlapping, and only one peak is shown in steady state emission spectrum. Based on the hardware analysis of phase fluorometry,by selection of the detector phase angle,the emission from various components could be individually suppressed. If the 5.9 ns component was suppressed, the emission spectrum was red-shifted. On the contrary, the emission spectrum was blue-shifted when 73 ns component was suppressed. Based on the software analysis, the individual emission spectra were resolved with three lifetime components by measuring phase and modulation data at various wavelength. Compared with steady state spectrum,the emission maximum wavelength of 5.9 ns component was blue-shifted from 68nm to 680 nm,but those of 24 ns and 73 ns components were red-shifted to 685 nm and 683 nm respectively.