To　study　the　dynamic　mechanical　properties　of　LY315　steel　at　different　temperatures　and　strain　rates,　a　split　Hopkinson　pressure　bar　(SHPB)　system　was　used　to　carry　out　dynamic　impact　tests　on　LY315　steel.　Quasi-static　(strain　rate　0.　001　s　-　1)　compression　tests　were　also　conducted　using　the　DNS100　electro　mechanical　universal　testing　machines,　and　the　stress-strain　curves　under　different　test　parameters　were　obtained.　The　experimental　results　show　that　LY315　steel　has　an　obvious　strain　rate　strengthening　effect　and　temperature　softening　effect.　At　high　strain　rate,　when　the　temperature　is　below　400　℃,　the　flow　stress　decreases　obviously　with　the　increase　of　temperature,　showing　a　significant　temperature　softening　effect.　When　the　temperature　is　above　400℃,　the　material　shows　the　third　strain　aging　phenomenon,　which　is　most　obvious　at　600℃　.　Based　on　the　test　results,　a　modified　Johnson-Cook　dynamic　constitutive　model　for　LY315　steel　was　proposed,　which　can　reflect　the　material　dynamic　mechanical　properties　well.　The　study　results　can　provide　a　reference　for　the　dynamic　analysis　of　the　steel　at　high　temperature　and　high　strain　rate.　©　2023　Science　Press.　All　rights　reserved.