Abstract:Twentytwo species in four genera of Mniaceae are reported from Bailong River Basin of Gansu. Four of them, Plagiomnium venustum, Rhizomnium magnifolium, R.striatulum and R.tuomikoskii are reported from Gansu for the first time. The keys to the genera and species and distribution and habitats for each species are presented. Meanwhile the geographical elements of family Mniaceae are analyzed.