Abstract: Glochidia of six unionid species, Lanceolaria eucylindrica Lin, L. gladiola (Heude), Lamprotula caveataLamprotula caveata (Heude), L. cornuumlunae (Heude), Hyriopsis cumingii (Lea), Cristaria plicata (Leach), were studied under optical and scanning electron microscope (SEM). The materials for the study were derived from mature shells collected from Poyang Lake, Jiangxi Province in 1996-1997.The marsupia f adult Lamprotula caveataLamprotula caveata and L. cornuum-lunae are formed by joining all four demibranchia while those of the other species are formed merely with two outer demibranchia. The conglutination was observed only in two Lanceolaria species. The differences in glochidia among species are obvious. The glochidia of Lanceolaria eucylindrica, L. gladiola and C. plicat are hooked, and the rest are hookless. In the hooked forms, the glochidia of C. plicat are obviously large and each has four pairs of sensory hairs. The other two species have three pairs of sensory hairs, but L. gladiola differs from L. eucylindrica by having asymmetric shells.All hookless glochidia have semi-elliptical appearance. However, the shell surface of Lamprotula caveataLamprotula caveata has shallow pits while those of the other two have pores. Sensory hairs are also different in number. Four pairs were observed in Lam. caveata and Lam.cornuum-lunae, but only two pairs were found in H. cumingii.