Abstract: The Lancangjiang Nature Reserve has been focused attention at both home and abroad that possesses international significance. This nature reserve makes invaluable contribution to the ecological security in the Greater Mekong Sub-region for its special location and the biodiversity. The protection of rare and endangered plants is commonly taken as a symbolic feature for the conservation of local forest ecosystem and species diversity. The endangered plant species in the nature reserve were studied by sample plots, volutes and surveys. The results are as follows:There were 23 rare and endangered plant species and 1 variety in the reserve. The rare and endangered species were mainly distributed in the semi-humid evergreen broad-leaved forest and the mid-mountain humid evergreen broad-leaved forest at the altitude of 1450~3100 m. In terms of the life forms, there were 20 endangered woody plant species, accounting for 21.3%~26.0% of the forest ecosystem, while there were 3 herbaceous plant species endangered. The study showed that the forest ecosystem in the nature reserve was severely threatened by activities of human beings.