Transmission electron microscopy and light microscopy are used to view the development of microga-metophyte and sperm in Isoetes sinensis and I.yunguiensis.The results show that:(1)lifetime of microgametophyte in the two quillwort species are only 15-30 d,live in sporoderm all life;(2)male gametophyte are consistes of 1 prothallial cell,1 antheridium wall cell and 4 sperm cells.There are plentiful inclusion in prothallial cell and antheridium wall cell;(3)sperm consists of nucleus,flagellum,microtubular ribbon and cytoplasm;(4)the gemination rate of microspore in I.sinensis is 4.5%,producting average 0.46 sperm per microgametophyte,swimming speed of sperm is 53 μm/s and lifetime of sperm is 8 min.The gemination rate of microspore and production of sperm in I.yunguiensis are higher than that in I.sinensis,but swimming speed and lifetime are lower than that of I.sinensis.The primary reason of endangerment of quillwort in China attributes to the low production rate of spermatozoid limit of reproduction and ecology and water pollution.According to the characteristics of male individual,Isoetes are higher than other Lycophytes.The development pattern of Isoetes male gametophytes was summarized.