Ethnic knowledge has been formed through the accumulation of experiences from practical activities in the specific ecological environment in which the ethnic community has lived and has been passed on from this generation to others. This knowledge is the basis for the community to make decisions related to life, especially in issues for instance exploitation, management, conservation of natural resources, health issues, and also in management of social activities. The Mnong in Dak Nong are considered a local minority. They have relied on the natural forest environment by clearing land to grow crops and exploiting forests products to serve their daily life for a long time. Thus, they have created a knowledge system for the natural exploitation of forests. However, in the development process, this knowledge system also changes over time. With data collected from the community, we identify this knowledge system in the tradition, simultaneously point out some different changes in this knowledge system at the present.