This work examined the background of the Lua ethnic group and whether and how the group was related to other related ethnic groups. To clarify to this doubt, a documentary research study was conducted on the Lua, Lavua, Palaung, Da Ra-ang, Mlabri and Khmu groups. A part of the data was derived from the fieldworks and academic talks on these ethnic groups by specialists. The study indicated that investigations on ethnic languages, backgrounds and legends must be conducted. Although some of them shared the same legends and heroes, a cultural and linguistic distance might have developed when they resided in separate geographical areas. The same group might differ linguistically after a period of time living in different villages or towns. Their different lifestyles might have been caused by separate political, historical, traditional and cultural changes from the past to the present.