How　displacement　damage　defects　generate　and　evolve　in　materials　irradiated　by　energetic　particles　is　a　perennial　topic　in　the　field　of　nuclear　materials.　Here　we　experimentally　reveal　the　dynamic　equilibrium　of　displacement　damage　defects　at　room　temperature　and　their　subsequent　influence　on　deuterium　retention　in　tungsten.　As　irradiation　dose　increases,　the　major　interstitial-type　defects　transform　from　dislocation　loops　(＜=　0.1　dpa)　to　dislocation　lines　(0.1-0.15　dpa)　and　then　to　dislocation　networks　(＞=　0.15　dpa),　and　finally　the　dy-namic　equilibrium　of　defects　featured　by　a　stable　microstructural　configuration　of　the　coexistence　of　networks　and　loops　is　reached　(＞=　0.2　dpa).　In　contrast,　no　significant　changes　in　the　dominant　category　of　vacancy-type　defects　are　observed　above　0.05　dpa　due　to　the　higher　migration　barriers　of　vacancy　clusters　than　interstitial　clusters　at　room　temperature.　The　defect　dynamic　equilibrium　is　confirmed　via　multiple　results:　the　damage　microstructure　asymptoticly　reaches　a　steady-state　expressed　by　a　constant　density　and　size　of　defects,　the　hardness　does　not　increase　anymore,　and　the　deuterium　retention　saturates.　The　nature　of　defect　dynamic　equilibrium　is　that　the　generation　and　annihilation　of　radiation　defects　restrict　each　other　so　that　total　defect　content　approaches　an　approximate　constant　under　continual　irradiation.　Besides,　we　also　verified　the　saturation　of　deuterium　retention　is　inseparable　from　the　defect　dynamic　equilibrium　in　a　highly　irradiated　tungsten.　These　findings　will　convey　some　fresh　insights　into　defect　evolution　and　fuel　inventory　in　tungsten　and　even　other　materials　in　the　limit　of　high　doses.