Due　to　the　rapid　growth　of　the　number　of　vehicles,　Beijing　has　implemented　license-　plate　lottery　policy　to　control　the　number　of　vehicles　increasing　since　2011.　In　order　to　solve　the　problem　that　some　groups　of　people　participated　for　a　long　time　but　never　won　the　lottery,　the　＇ladder　probability＇　rule　has　been　implemented　since　2014.　However,　the　effect　is　not　significant.　This　paper　establishes　an　evolutionary　model　to　describe　the　probability　change　of　different　groups　based　on　the　analysis　of　the　current　license-plate　lottery　rule　in　Beijing.　The　rationality　of　the　current　＇ladder　probability＇　is　analyzed,　and　the　improved　＇ladder　probability＇　rule　is　proposed.　Through　the　analysis,　it　is　found　that　the　current　＇ladder　probability＇　rule　could　not　continuously　improve　the　winning　probability　of　earlier　participants,　the　main　reason　is　that　the　degree　of　probability　improvement　is　insufficient.　The　improved　＇ladder　probability＇　rule　can　increase　the　winning　probability　of　all　groups　with　time　when　the　adjustment　intensity　is　reasonable.　The　disadvantage　of　this　rule　is　that　it　reduces　the　winning　probability　of　new　participants　in　the　current　period.　The　research　conclusions　provide　theoretical　support　for　managers　to　carry　out　scientific　license-plate　lottery　policy.　Copyright　©　2019　by　Science　Press.