Abstract: The pollen and pollination tenhnique of cross breeding in Liriodendron was studied.The results show that:(1)The pollen quality of interspecies and individuals of intraspecies is quite different. The quality changes during the flowering period.It reaches the highest level in the middle stage of flowering period;(2)If the pollen is stored in 4?℃ condition,the survival rate will dropped quickly.So,it is better to use fresh pollen for cross breeding.(3)The filled samara rate of artificial pollination varies during the flowering period and in different time of a day. It is highest in the middle 10 dayes of flowering period and about 1PM. (4)In the early and late stage of flowering period,pollination bags can improve the filled samara rate of controlled pollination.Theirfore,in this period,the artificial pollination should be carried out at 1PM and baged.While,in the middle 10 dayes of flowering peiod,the artificial pollination can be done at any time of a day and neednt bag. The contamination rate is less than 1%.