Abstract: A solidified hook was found by observing the macrostructure of a leaked strand.The general formation theory of solidified hook is revised in this paper.It is pointed out that during vibration of the mold,the existence of the negative slip results in variation in temperature in the solidified front and pressure in the molten slag channel which constitutes the main reason for formation of the solidified hook.The varying pattern of the pressure in the protecting slag channel of the casting mold is analyzed,through which the validity of the revised theory can be proved.It can be concluded that by adjusting steel temperature,smoothening the running condition of the mold and choosing reasonable protecting slag,the formation of solidified hook can be avoided.