Abstract: The research results show that under osmotic stress at -0.73MPa caused by PEG-6000(25%,w/v),the content of water in seedlings is decreased,and the content of CaM(Calmodulin)in leaves increases rapidly,and reaches the higher level at 12h of stress,is lower than that of the control afterwards;however,the content of CaM in roots decreases at 12h of stress,and then increases to a peak at 48h,and declines quickly in the end.Under the above osmotic stress,the addition of exogenous CPZ(100μmol/L),a CaM antagonist,can decrease obviously the relative water content (RWC)and dry matter weight of leaves,enhance the membrane permeability,and also inhibit the elongation of leaves and roots.