The authors investigated the fish resources in the Dulong River, Irrawaddy basin from October to November, 2004. Twenty six sampling sites were established and 883 fish specimens were collected in different altitudes and habitats. The analysis revealed that: (1) the fish biomass in both the main stream and its tributaries descend when the altitude ascends; (2) fish species diversity descends when the altitude ascends. The Shannon-Wiener index and the species evenness in the main stream are higher than those in the tributaries; (3) except for Schizothorax
) dulongensis and Oreoglanis macropterus
, the occurrences of all the other five species are significantly related to the changes in altitude.