The vitality and cell structural changes of the lichen samples treated with different concentrations of CuSO₄ (0,1,2,3,4 mmol/L) after 24 h were studied by using light microscopy and ultrathin sections of transmission electron microscope,respectively,to find out the effects of Cu²⁺stress to the cell structure.Results showed that:(1)The vitality of Ramalina sinensis photobionts was decreased with the upgrade of the treated Cu²⁺ concentration,but the photobionts vitality of Peltigera rufescens seems to be remain stable.(2)No obvious changes in the cell wall,cell membrane,mitochondria and chloroplast were detected in Ramalina sinensis symbiont under low Cu²⁺ concentration(＜1 mmol/L) treatment group.Distinct damages,especially to cell membrane and organelles such as mitochondria and chloroplasts were observed in upgraded Cu²⁺ concentrations(＞2 mmol/L).It is clear from the results that higher the concentrations,stronger the damages.(3)In the other studied lichen species,P.rufescens which were treated with Cu²⁺ completely same as R.sinensis,no any damages can be detected even in the higher treatment group.In contrast,numerous of the dividing cells were observed,that suggest Nostoc photobionts of P.rufescens seems to be more tolerant than Trebouxia photobionts of R.sinensis to higher concentration Cu²⁺ treatment.