In the perspective of asexual reproduction,the development process of critically endangered level (CR) Isoetes sinensis plant sporangium was continuously observed with method of semithin-section to provide intuitive and reliable theoretical basis for investigating the reasons for its endangered.The result showed that:(1)Megasporophyll and microsporophyll of I.sinensis are alternate arranged,no mixed sporangium.(2)Supplying the nutrients for the spores by septum filament.The size of paraphysis is critical to the size,productivity and fertility of spores.(3)The microsporangia are uniformly developed,while the megasporangia are nonuniformly;both kinds of sporangia present almost 50% abortion.(4)Both kinds of sporangia have no sporangiophore and no annulus also.The spore release depends on sporangium decompose.It suggested that the developing characters of sporangium is one of the endangered reason for I.sinensis due to high abortion rate of sporangia,no release structure or highly environment dependence.Comparing with relative species sporangium,it could be found that only Isoetes spores spread borrowing outside force and the higher requirement on the habitat,which verified the status of Isoetes old system and illustrated the Isoetes has more abilities of monitoring environmental indicators in habitat area.