Abstract: The main roots in root system of diversifolious polar can＇t well develop when ground water level become high and the air can’t open in soil, but side root system in low layers is main in its root system.When grownd water level become low and the air was improved in soil, it grow next side root, straightening down over side root of lower layers and stretch to deep layer under ground.When roots of populus diversifolia was wounded or broken, it can grow new branch from wound organization or nearby broken roots and form new root system in new branch, it is as same as cuttage.