Abstract: Based on the materials collected from November, 1988 to December, 1993 and the deposited specimens, the present paper primarily deals with the interspecific differentiations between Yunnanilus pleurotaenia and Yunnanilus chui in Fuxian Lake, referring to their morphological characters, living spaces, diets, age and growth, breeding babits. The investigation reveals that the interspecific differentions in morphology of two Yunnanilus species appera mainly in SL/body depth, head length/eye diameter, length of caudal peduncle/ depth of caudal peduncle, mouth situation, length of maxillary barbel, number of branched dorsal fin rays. The loach Ynnanilus pleurotaenia lives mainly in the streams flowing into or out the lake as well as their outlets and inlets, feeding mainly on Gammarus sp. and chironomid larvae, having a higher growth rate and absolute fecundity than Yunnanilus chui. The loach Yunnanilus chui lives mainly in the vegetations of vascular hydrophytes occurring in the coastal area of the lake, feeding mainly on zooplanktons, having a lower growth rate and absolute fecundity than Y. pleurotaenia. Two Yunnanillus species share the following common features in breeding: eggs are fairly small, the relative fecundities very high and females greatly dominant in their populations. These features can ensuure that their populations have potentially high abilities in breeding.