Abstract:New megaspore morphological characteristics of the protected plant—Isoetes yunguiensis were observed using scanning electron microscope (SEM). The result indicates: globular granule on megaspore surface; inapparent reticulate ornamentation; inapparent reticulate ornamentation with big size. Megaspore of the old ligulate heterosporophyte are easy to significantly change in size, ornamentaion and fissure.