Abstract: A cyto-embryological observation has been made by using the hemalum-methyl salicylate stain-clearing technique and paraffin section method. It is discovered that there is a low frequency of apomixis in APⅣ, a indica rice twin seedling line.The results of research on origination of adventive embryony have indicated that: One day before flowering, the nucellus contain some expanded cells possessing big and significantly heavily stained nucleus, this kind of cells could develop into nucellar proembryony. The spherical adventive embryony proliferated into embryo sac cavity along with the nucellus degenerating and differentiation of these spherical adventive embryony began four days after flowering, Adventive embryony can survive in the embryo sac cavity with or without zygote embryo, But the double embryo most partly formed from the cleaving of zygote embryo or from the fertilized synergid, The spherical hard stained structure in the endosperm sac cavity, originated from the dropped endosperm part, is not adventive embryony. The antipodal cells at the mieropylar border can not form embryo.