Abstract: Lhasa River is the biggest tributary of Yarlung Zangbo River. Its fish fauna comprise 13 fish species and a natural bastard, belonging to Schizothoracinae, Nemacheilinae and Sisoridae. Disturbed by human activities, plenty of exotic fishes have been found in Lhasa River in recent decades. Moreover, the fish resources of Lhasa River are under overfishing. Most of the endemic fishes grow slowly and mature late, so they are very vulnerable to invasions of the exotic fishes and overfishing, and the populations can not be replenished easily if depleted. So the investigation and protection strategies of fishes of Lhasa River are very important and urgent works. We roundly investigated the fish resources of Lhasa River with floating net, gill net and set net during Apr. to Jun. in 2004, Sep. in 2004 to Jan. in 2005, Mar to Apr. in 2005, May to Sep. in 2006. This paper introduced the result of our investigation. It was found that there were 8 exotic fish species (Carassius auratus (Linnaeus), Pseudorasbora parva (Temminck et Schlegel), Misgurnus anguillicaudatus (Cantor), Hypseleotris swinhonis (Gunther), Cyprinus (C.) caupio Linnaeus, Ctenopharyngodon idellus (Cuvier etValenciennes), Carassius auratus gibelio (Bloch), Silurus asotus Linnaeus, and 2 species indeterminate, and 14 fish species (Schizothorax waltoni (Regan), S. o'connorii (Lloyd), S. macropogon (Regan), Ptychobarbus dipogon (Regan), Oxygymnocypris stewartii (Lloyd), Schizopygopsis younghusbandi younghusbandi Regan, Triplophysa stewartii (Hora), T. stenura (Herzenstein), T. tibetana (Regan), T. orientalis (Herzenstein), T. stoliczkae (Steindachner), T. brevicauda (Herzenstein), Glyptosternum maculatum (Regan), and a natural bastard of S. waltoni and S. o'connorii). These 14 fish species were also found by previous researchers. As to the species indeterminate, species indeterminate A looked like O. stewartii and also looked like S. y. younghusbandi, so it might be omitted by the former investigator; species indeterminate B was very rare and it had many medial morphological characters of species indeterminate A and O. stewartii, so it might be omitted by the former investigator or a new natural bastard. We analyzed the distribution of economic fishes of Lhasa River. S. y. younghusbandi and P. dipogon were dominant species in Lhasa River, especially in the upstream; O. stewartii mainly distributed in the downstream; S. o'connorii was rare in winter; S. waltoni and S. macropogon were rare in Lhasa River. We inferred that S. o'connorii, S. waltoni and S. macropogon mainly inhabited in Yarlung Zangpo River and migrated to Lhasa River to spawn during spawning season. As to the exotic fishes, C. auratus, P. parva and M. anguillicaudatus were majority and distributed widely; C. (Cyp.) caupio and H. swinhonis increased quickly in amount; C. idellus, C. auratus gibelio and S. asotus were rare. We also pointed out that the two main threats to the fish resources of Lhasa River were decrease and miniaturization caused by overexploitation and invasion by alien fishes. In this paper, we analyzed and discussed the phenomenon and presented a series of strategies on how to protect and reasonably use of fish resources of Lhasa River: reasonable fishing, constituting fishing ban period, controlling alien fishes, protecting habitant of fishes and so on.