Abstract: The megasporogenesis and development of female gametophyte were studied by paraffin sections in line M14,a chromosome 9 monosomic addition line of Beta corolliflora Zoss.in sugar beet,in which revealed that the egg cell could been produced through diplospory or sexuality.The results are as follows:sexuality is of Polygonum-type,and diplospory is of two types,Allium odorum-type and Antennatia-type in M14.The megasporocyte of Allium odorum-type and Antennatia-type turn into a mature diplosporous female gametophyte.The Megasporocyte Polygonum-type turns into a mature monoplontic female gametophyte.Compared with the sexual female gametophyte,bradygenesis and abortion can be frequently observed during the development of diplosporous female gametophyte.Only 25% of them are normal.The characteristic of diplosporous reproduction is discussed.