In vitro experiments were carried out，regarded test-tube seedings of garlic stem tip as explants and took MS as the basic culture medium.The results showed that Within a certain range,raising concentration could inhibit the formation and differentiation of the bulb, the leaves and roots were shortened and widened. The 6mg?L-1 PP333 was the optimal treatment concentration of the inducing bulb formation and development. The endogene hormone content change showed that after PP333 treatment, in the garlic test tube seedlings leaf sheath the IAA/ABA ratio drops suddenly，and reduces the scope to be bigger, the bulb forms expands the effect to be better.