To　reduce　the　aerodynamic　drag　of　the　vehicle,　three　kinds　of　riblet　shape　non-smooth　surfaces　were　arranged　in　the　tail　of　the　Motor　Industry　Research　Association　(MIRA)　stepped-back　vehicle　mode.　The　shapes　of　the　non-smooth　riblet　elements　are　triangular,　circular　and　rectangular.　Computational　fluid　dynamics　(CFD)　method　was　used　for　numerical　analysis.　To　verify　the　effectiveness　of　the　analysis　method,　the　analysis　result　of　the　standard　MIRA　stepped-back　vehicle　mode　was　compared　with　wind　tunnel　test　data.　The　tail-flow,　pressure　and　turbulent　kinetic　energy　of　the　MIRA　stepped　back　vehicle　modes,　which　were　arranged　with　riblet　elements,　were　analyzed.　The　effects　of　riblet　shape　of　non-smooth　surfaces　on　the　reduction　of　vehicle＇　aerodynamic　drag　were　compared　with　each　other.　The　simulation　results　show　that　the　three　kinds　of　non-smooth　surfaces　have　a　good　effect　on　drag　reduction　by　reducing　the　negative　pressure　in　the　tail　zone　of　the　model,　reduce　the　turbulent　kinetic　energy　and　reduce　energy　dissipation.　The　circular　non-smooth　surface　is　better　than　the　other,　with　drag　reduction　effect　of　5.53%.　©　Published　under　licence　by　IOP　Publishing　Ltd.