Abstract: The declining cause of varietal vitality is discussed in winter wheat．The results show that the bumper and stability of the wheat mainstay varieties "12057”,“Jinmai 33" and "Jinmai 47”depend on their bigger variation of ear numbers and stable grain weights pear and 1000 kernel weight．The main cause of varietal vitality decline is due to the loss of its resistance．The life cycle of varieties is divided into superiority stage，adaptation stage of variety and environment，and variety decline stage Al1 varieties possess the effect of time and space.