Chlorophyll-fluorescence were measured by a handy PEA fluorometer in moss Plagiomnium cuspidatum (Hedw.) T.Kop. in response to a mixture heavy metal cations of Cu2+，Zn2+, Cd2+ and Pb2+ at concentrations of 0, 1, 5, 10, 50 and 100μmol/L respectively. Exposure in a mixture heavy metal solution 10-day period resulted in a decline of chlorophyll fluorescence and content of chlorophyll. Heavy metals used within 10μmol/L，a little change of all the analyzed values of Fv/Fm、ETo/ABS、ETo/TRo and RC/CSo was observed compare with controls, but a dramatic decrease occurred when the metal concentration increased to 50 and 100μmol/L.The result indicated that the photosynthetic apparatus of the moss Plagiomnium cuspidatum was not badly damaged when the mixed-heavy metal solution became lower than 10μmol/L concentrations, but the damage was not reversible up to 50 or 100μmol/L.