Pool planting experiments of three poplar clones from Aigeiros section under flooding and waterlogging condition showed that, in comparison respectively with their controls, the accumulation of abscisic acid (ABA），protein in leaves and the production of ethylene in basal stems of all clones tested increased obviously, but the content of zeatin riboside （ZR） in leaves decreased obviously. There existed some differences among seedlings of various poplar clones. By comprehensive consideration of the morphology and the growth of three clones, it was suggested that increase of ABA might be an effective strain of poplar seedlings for flooding stress. Multiplication of ethylene when seedlings were in flooding stress promoted the basal stems to form the succeeding adventitious roots, therefore the content of ZR was increased. It was more important that the flooding and waterlogging endurence for the poplar clones could be the change range of the physiological index (ABA, ZR, protein and ethylene) compared with that of control, and the abilities of the physiological properties to return to normal.According to the data observed from the experiment about the effects of stress on the physiology and the biomass of three poplar clones seedlings, it was known that the water resistance of clone Ⅰ－69 was the highest under the flooding stress, however, that of clone Ⅰ－351 was the highest under the waterlogging stress.