In order to study the responding of different growth state on low temperature in Broccoli (Brassica oleracea var. italica), we took prematurity broccoli hybrid as the objects. It was found that growth state was varied under different sowing time , moreover, stem became wider with the increasing of light density at the same leaf age.Seedling age of responding to low temperature vernalization only when they grew five leaves above and with over 3.03± 0.07 centimeter stalk width in "Qingfeng Broccoli 103". The older leaf age was and the stronger plant was, the more sensitive and the shorter demanded duration time on low temperature was, and the shorter time required when the plants entered into critical period of floral bud differentiation.