Abstract: The megasporogenesis and development of female gametophyte in Eunymus japonicus were studied by the parraffin section method.The results areas follows:①The ovule is crassinucellar,the nucellar epidermal cell cuts off several layer nucllar parietal.The ovule is bitegminy,anatropous and orthotropous.The micropyle is made up of an outer and inner integument;②A single archesporal cell differentiates immediately below the nucellar epiderm,it functions directly as the megaspore mother cell.During megasporogenesis,the dyad cell near micropyle doesn’t divide,however,the other cell beside the chalaza splits nomally,thus it makes megaspore triad,the triad arrange in a straight line or in a"T"shape;③Its embryo sac is Polygonum type.The mature embryo sac has seven cells and eight nuclei or seven nuclei,and a cap shaped hypostases is present in mature ovule.Two polar nuclei fuse into the secondary nucleous.Three antipodal cellls degenerate lately.