OBJECTIVE： To study the regularity of Glycyrrhiza uralensis， and to provide theoretic basis for cross breeding of G. uralensis. METHODS： The flowering sequence of G. uralensis was observed， as well as the correlation of flower external morphology and internal structure， flowering rush hour a day， flower blooming dynamics. At the same time， pollen-ovule ratio （P/O） and pollen viability at different flowering periods were determined. RESULTS： Flowers on main stem firstly bloomed， the opening order was bottom-up， and when three to five flowers bloomed， the lateral branch began to bloom， which order was also bottom-up. There was a closely correlation between the situation of pollen shedding and the size of banner blooming. 10：00-13：00 and 15：00- 18：00 were flowering rush hour. A flower from bloom to closed needed about 32 hours， wilting about after 35 hours. P/O＝260.46， it was facultative xenogamy. When banner bloomed 2-5 mm， the pollen had the highest life force. CONCLUSIONS： The results can guide the sexual hybridization breeding of G. uralensis， and lay a good theoretical basis for its new varieties breeding.