Tropical forests are characterized by very high plant diversity but they are also threatened by forest degradation and deforestation. In this regard, Southeast Asia has the highest relative rate of deforestation in the world and therefore, Laos, which is not an exception, suffers forest degradation and deforestation. This study was carried out in Phou Khao Khouay Protected Area in Laos which was intensively logged in the past and where roads and villages continue to threaten the biodiversity of the forest. Thirty-two permanent plots of 0.25 ha were established along an altitudinal gradient in order to understand the environmental and human influence on forest composition, structure and diversity. Co-inertia analyses allow six forest types to be described in terms of floristic composition, structure and soil preference. Thus, the ecology of species and evolution of forests after disturbance is evaluated. This can provide knowledge for better management of the forests in Phou Khao Khouay National Biodiversity Conservation Area.