Abstract: Changes in the content of endogenous polyamines and malondialdehyde (MDA) responding to salinity stress and effects of exogenous polyamines and the polyamine biosynthesis inhibitor on polyamines and malondialdehyde (MDA) content were investigated in leaves of 1yearold Malus hupehensis Rehd. seedlings grown in hydroponic systems. Results showed that the content of free putrescine (Put) was increased, and the content of free Spd and Spm and (Spd+Spm)/Put ratio in leaves were significantly decreased under salt treatment. Accumulation of MDA was significantly decreased treated with exogenous Spd or Spm under salt stress. Moreover, the polyamine biosynthesis inhibitor aggravated the lipid peroxidation caused by salt stress in M.hupehensis, and the content of MDA was increased markedly. It suggests that spermidine and spermine could alleviate the damages on lipid peroxidation induced by salt stress in M.hupehensis.