Abstract: In order to clarify the characteristics of flower bud differentiation of Hippeastrum hybridum and provide theoretical basis for the research of flower development,flowering regulation,cross breeding and systematic classification,anatomical observation and paraffin sectioning techniques were used to study the growth of flower buds,flower organ differentiation,and sex cell differentiation in the H. hybridum variety of‘Merry Christmas’. The main results were as follows:Each year H. hybridum‘Merry Christmas’ produced two inflorescence buds,the flower buds in which completed floral organs differentiation in the second year,then bloomed in the third year after low temperature treatment,and of which the second inflorescence aborted occasionally. The floral organ differentiation process included flower primordium differentiation stage,outer perianth primordium differentiation stage,inner perianth primordium differentiation stage,stamen primordium differentiation stage and carpel primordium differentiation stage,the corresponding length of flower buds were about 0.02,0.05,0.1,0.2,0.3 cm,respectively. The primordia of all floral organs initiated spirally and centripetally. The anthers of H. hybridum were tetrasporangiate,and the anther wall was composed of epidermis,endothecium,middle layer,tapetum from outside to inside. The tapetum belonged to secretory type.The cytokinesis in the microsporocyte meiosis was successive. The microspore tetrads were cruciform and the mature pollen grains were 2-celled. The gynoecium of H. hybridum was tricarpellary and the ovary was inferior with axile placentation and trilocular with two rows of anatropous ovules in each locule. The ovule was bitegmic and crassinucellate. The development of embryo sac was of an Allium type.