Mossbauer spectrum measured for the iron components of photosystem Ⅱ (PS Ⅱ ) particles of spinach is a superposition of 4 doublets. Quadrupole splitting and chemical shifting of doublets I -IV are characteris-tics of proteins with oxidized cytochrome b-559, reduced cytochrome b-559, Fe3 + -Q complex and Fe2+ -Q complex re-spectively . After the PS II particles are treated with La3+ , two doublets of Fe2+ disappear and Fe2+ is converted into Fe3+ , indicating that the reduced cytochrome b-559 has been converted into the oxidized cytochrome b-559, and Fe2+-Q complex into Fe3+-Q complex. The Mossbauer spectrum of PS II particles treated with La3+ and Ca2+ shows that Ca2+ can weaken the inhibitory effect of La3+ in part, and a portion of the reduced cytochrome b-559 and Fe-Q complex still exist. Mossbauer spectrum measured for the iron components of photosystem II (PSII) particles of spinach is a superposition of 4 doublets. Quadrupole splitting and chemical shifting of doublets I -IV are characteris-tics of proteins with oxidized cytochrome b-559, reduced cytochrome b -559, Fe3 + -Q complex and Fe2 + -Q complex re-spectively. After the PS II particles are treated with La3 +, two doublets of Fe2 + disappear and Fe2 + is converted into Fe3 +, indicating that the reduced cytochrome b-559 has been converted into the oxidized cytochrome b-559, and Fe2 + -Q complex into Fe3 + -Q complex. The Mossbauer spectrum of PS II particles treated with La3 + and Ca2 + shows that Ca2 + can weaken the inhibitory effect of La3 + in part, and a portion of the reduced cytochrome b-559 and Fe-Q complex still exist.