The aim of this study was to find the relationship between megasporogenesis, development of female gametophyte and morphological changes of flower, ovule in Siraitia grosvenorii. The ovaries were observed under light microscope by means of paraffin wax fixation. The results showed that ovule of Siraitia grosvenorii was anatropous, bitegmic and crassinucellar. The chalazal megaspore of linear tetrad developed into Polygonumtype embryo sac. Morphological changes of flower and ovule indicated different developmental stages of megasporogenesis and female gametophyte. As the length of ovary ranged from 7 to 9 mm and the nucellus were oval-shape, 45.83% megaspore mother cells were at the stage of meiosis. These suggested that the morphological characteristics of flower and ovule could be used to distinguish different stages of megasporogenesis and female gametophyte development of Siraitia grosvenorii.