Displacement　damage　induced　by　space　radiation　is　still　a　considerable　challenge　of　expanding　application　of　GaAs-based　devices　(e.g.　solar　cell,　et　al.)　in　space　missions.　In　the　current　work,　molecular　dynamics　(MD)　simulations　are　applied　to　investigate　displacement　cascades　evolution　in　GaAs　at　room　temperature.　A　set　of　displacement　events　initiated　by　different　energies　(up　to　50　keV)　of　primary　knock-on　atom　(PKA)　were　simulated.　An　improved　Wigner-Seitz　(W-S)　cell　method　was　developed　by　introducing　a　simple　criterion　for　more　accurate　identification　of　interstitials　and　antisites.　Based　on　the　present　defect　analysis　method,　the　generation,　evolution　and　distribution　of　point　defects　were　discussed　at　first.　Then,　the　mechanisms　of　both　vacancy　and　interstitial　cluster　evolutions　along　simulation　time　were　presented.　The　results　indicate　that　both　Ga　and　As　type　defects　play　the　same　crucial　role　among　interstitials,　antisites　and　vacancies.　As　the　energy　of　PKA　increases,　the　start　points　of　heat　spike　phase　postpone　slightly.　Moreover,　the　non-linear　increase　of　surviving　defects　accompanied　with　the　rise　of　the　energy　of　PKA　is　considered　as　contribution　of　directly　amorphous　pockets.　During　the　stage　of　cascade,　as　time　progresses,　different　size　clusters　show　up　in　succession　from　small　size　(i.e.,　between　2　and　5)　to　larger　size.　The　medium　and　large　vacancy　clusters　virtually　only　exist　in　the　middle　of　cascades,　and　the　majority　of　vacancies　belong　to　the　categorizes　of　single　vacancy　and　small　clusters,　especially　at　the　end　of　cascades.　However,　the　medium　and　large　interstitial　clusters　incline　to　hold　up　or　grow　continually　at　the　MD　time　scale　once　they　build　up.　Meanwhile,　interstitials　in　larger　clusters　(30　∼　)　account　for　more　fraction　as　the　energy　of　particles　increases.　©　2021　Elsevier　B.V.