In this paper,the base of mature leaves of three Chinese Isoetes are used as experimental materials.With the method of paraffin technology,we observed three Chinese Isoetes ligules in detail to build their own stereoscopic models,and analyzed the genetic relationship between them.They were compared with Central Asia and North American Isoetes ligules to discuss the evolutionary relationship.The results show that:(1)All three Chinese Isoetes ligules had tongue,glossopodium and medimoles.(2)Both Isoetes sinensis and I.orientalis ligules had side tongue like halberd-shape,oval-shape cornua and glossspodium paraller with leaf axis.Oppositely,I.yunguiensis had long nose-shape tongue without side tongue,triangular cornua and glossopodium angled with leaf axis.(3)The lateral view of I.sinensis and I.yunguiensis glossoposium were oblong,but I.orientalis was reniform.The study suggests that the genetic relationship between Isoetes sinensis and I.orientalis is close,and they two are distant with I.yunguiensis.The ligule should be coalescent form of Isoetes.With its complex structure and stable obvious difference,ligule is suggested to be a important gist in Isoetes classification.