Ultrastructure of spermatozoon of Hucho taimen in Wusuli River was observed by transmission electron microscopy. The spermatozoon of Hucho taimen consisted of a head, a midpiece and a tail. The head was ovoid in shape, of which the main structure was nucleus. It had no acrosome and at its caudal end the nucleus had an implantation fossa. The nucleus consisted of electron dense chromatin materials and contained irregularly netlike gap. The midpiece consisted of the centriolar complex and the sleeve. The proximal centriole, which is made up of nine triplets of peripheral microtubules, and the distal centriole were arranged at a right angle to each other. The sleeve, which contained a high number of mitochondria and vesicles, was connected to the posterior end of the nucleus. Some of the single mitochondria were fused with each other and formed a complex chondriosome. The main structure of the tail was axoneme, which was slim and long. The structure of the tail was of the typical “9+2” model. At the proximal end of the tail there were many vesicles outside the axoneme. The distal end of the tail, however, did not contain any vesicles. The tail had lateral fins, which were undulating and arranged symmetrically.