Abstract: Changes in biochemical composition and enzyme activity were investigated during seeds stratification under nature temperature. The results indicated that crude fat and protein constituted the bulk of the storage reserves in mature seeds of Cyclocarya paliurus, accounting for 50% and 45% respectively. During stratification, the content of crude fat, soluble protein and starch all gradually declined, but the content of soluble sugars obviously increased. The activities of all the studied enzymes in the stratified seeds increased significantly as compared to those in control ones. The increased total activity of the lipase, amylase and protease was concurrent to degradability of fat, starch and protein, indicating that the substance and energy for germination of seeds were being well prepared. The results would provide an useful reference to find out the germination physiology of C. paliurus seeds.