Abstract:In order to understand the dominant species and water tolerance of aquatic bryophytes in hydro- fluctuation belt of Lengshui River Nature Reserve, Guihzou, China, the contents of Chl a+b, methane dicarboxylic aldehyde (MDA) and soluble sugar, and activities of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) of five dominant bryophytes were determined, and their water tolerances were evaluated. The results showed that there were 11 dominant bryophytes in Lengshui River Nature Reserve, in which Rhynchostegium riparioides, Palamocladium euchloron, Hyophila involute, Reimersia inconspicua and Fissidens grandifrons were the most dominant species with average dominance≥0.02. With the extension of waterlogging time, the content of Chl a+b in five mosses decreased significantly (P<0.05), and the contents of soluble sugar and MDA, activities of POD, SOD and CAT increased at first then decreased, showing strong water tolerance in five mosses for long term. The comprehensive evaluation value D of Rhynchostegium riparioides was the highest (0.953) by PCA and subordination function method. Therefore, it was suggested that Rhynchostegium riparioides had strong adaption to waterlogging, could be used as pioneer species in vegetation recover and restoration in hydro-fluctuation belt of Lengshui River.