Abstract: 【Abstract】  Five integral and active plerocercoids collected from naturally infected frogs were fixed by glutaraldehyde?-osmic acid， dehydrated in graded series of ethanol， dried via vacuum freeze and coated with carbon gold. They were then observed by scanning electron microscopy. The results showed that the anterior and posterior ends of the plerocercoids were slightly swell and without segmentation. Annular furrows ran irregularly along the body surface. The anterior end was drawn inside and had a deep dorsoventral hollow， around which， the plasma membrane displayed a lip bulge. The posterior end was similar to the anterior one in the shape， but a fissure in its central part was comparatively narrower and shallower than the hollow in the anterior end. There were thousands of pits and grooves on the body surface, unequal in size. The whole body surface of the plerocercoid was densely covered by sharp spine-like microtriches.

Key words: Rana nigromaculata, Plerocercoid, Scanning electron microscopy