Gudehus-Bauer　hypoplastic　constitutive　model　and　the　determination　of　its　parameters　are　studied　in　the　paper.　Confined　compression　test　is　used　to　determine　the　parameters　hs　and　n　of　hypoplastic　constitutive　model　for　rockfill　materials.　According　to　the　derivation　of　the　model,　the　relationships　between　the　parameters　α,　β　and　the　confining　pressure　are　established,　and　new　fitting　parameters　are　proposed.　Considering　the　dilatancy　for　rockfill　materials,　a　new　term　of　volumetric　strain　is　added　into　the　linear　term　in　the　model　with　a　good　fit　to　the　axial　strain-volumetric　stain　curve　of　triaxial　consolidated　drained　tests.　The　new　parameters　of　the　model　and　the　improvement　on　Gudehus-Bauer　hypoplastic　constitutive　model　are　verified　by　means　of　rockfill　large-scale　confined　compression　test　and　triaxial　consolidated　drained　tests.　Compared　with　the　test　results　of　rockfill　materials,　the　present　model　and　its　parameters　can　simulate　the　stress-strain　characteristics　of　rockfill　materials,　and　can　improve　the　simulated　axial　strain-volumetric　stain　curve.　Finally,　the　simulation　to　the　triaxial　consolidated　drained　test　in　loading-unloading　condition　by　the　improved　Gudehus-Bauer　hypoplastic　constitutive　model　is　carried　out,　and　the　results　show　that　the　improved　model　has　a　certain　application　of　unloading.　©　2018,　Science　Press.　All　right　reserved.