Two　multiaxial　damage　parameters　are　proposed　in　this　paper.　The　proposed　fatigue　damage　parameters　do　not　include　any　weight　constants,　which　can　be　used　under　either　multiaxial　proportional　loading　or　non-proportional　loading.　On　the　basis　of　the　research　on　the　critical　plane　approach　for　the　tension-torsion　thin　tubular　multiaxial　fatigue　specimens,　two　multiaxial　fatigue　damage　models　are　proposed　by　combining　the　maximum　shear　strain　and　the　normal　strain　excursion　between　adjacent　turning　points　of　the　maximum　shear　strain　on　the　critical　plane.　The　proposed　multiaxial　fatigue　damage　models　are　used　to　predict　the　fatigue　lives　of　the　tension-torsion　thin　tube,　and　the　results　show　that　a　good　agreement　is　demonstrated　with　experimental　data.