The megasporogenesis and development of female gametophyte of Prunus mahaleb Linn.were studied by using the method of paraffin section.The results indicated that:(1)During the early period of gametophyte of P.mahaleb,there were two anatropous ovules which were attached to the placenta,on the inner wall of its unilocular ovary.Later period,one of them degraded while the other developed into a seed.(2)It was a crassinucellate ovule with two integuments.Successive cytokinesis in the megasporocyte followed meiosis and the megaspore tetrads were linear.Function megaspore was in the chalaza and the monosporic embryo sac is polygonum type,Mature embryo sac had 7 celled and 8 nuclei.(3)According to the relationship between external morphological characteristics and internal anatomy observation of P.mahaleb at different time.We could know that late March is the most important time of the differentiation and development of female reproductive cells in the Guanzhong district of Shaanxi Province,It was time to strengthen the water and fertilizer management for the good quality and high yield of P.mahaleb.