Abstract: The origin, devlopment and structure of multiple embryo sacs in Kentucky Bluegrass( Poa pratensis L.)were studied.In an ovule, one to many aposporous initial cells around megasporocyte come from nucellus and may become into multiple embryo sacs.Only two of them can develop into mature one.The development of embryo sac of apospory is of Hieracium type.In the two mature embryo sacs, embryo and endosperm can be formed.Thus the pseudopolyembryony seed is formed.As to the middle embryo sac originated from nucellus, its embryo can be formed by apomixis.More than two multiple embryo sacs can not form mature one.