In　the　traditional　teaching　of　vibration　mechanics,　the　complex　modes　have　been　used　to　decouple　the　systems　as　a　manipulation　tool.　The　physical　meaning　of　the　complex　modes　is　not　clearly　transferred.　In　this　paper,　the　relationship　between　the　combo　of　displacement　and　velocity　of　every　oscillators　have　been　demonstrated　as　the　system　shows　the　complex　modes,　illustrated　by　a　2DOF　rotating　system.　The　non-uniform　and　following　features　of　the　complex　modes　have　been　discussed,　which　give　visual　physical　meaning　to　the　beginners　of　the　vibration　course.　©　2024　Chinese　Academy　of　Mechanics.　All　rights　reserved.