In　this　paper,　a　constitutive　model,　based　on　the　creep　deformation　mechanism　in　P91　steel,　under　a　wide　range　of　stress　levels,　was　established　and　embedded　into　finite　element　software.　The　accuracy　and　reliability　of　the　model　was　verified　by　comparing　the　simulation　of　uniaxial　creep　tensile　test　results　and　the　experimental　data　under　different　stress　levels　for　P91　steel　at　600　degrees　C.　The　creep　crack　growth　behavior　of　P91　steel,　under　a　wide　range　of　stress　levels　was　simulated　using　a　ductility-exhaustion-based　damage　model,　combined　with　the　stress-dependent　creep　ductility　model,　and　the　predicted　creep　crack　growth　(CCG)　rates　were　compared　with　the　experimental　data.　Finally,　the　established　model　was　used　to　predict　the　CCG　behavior　for　the　pressurized　pipes　with　axial　surface　cracks.　The　results　show　that　the　constitutive　model,　established　on　the　basis　of　the　creep　deformation　mechanism,　agrees　better　with　the　experimental　data　than　other　constitutive　models.　The　CCG　rate　varies　at　different　direction　angles　theta　for　the　axial　surface　cracks.　The　direction　angle　theta　corresponding　to　the　maximum　creep　crack　length　is　about　33　degrees,　when　the　internal　pressure　exceeds　10　MPa.　The　initial　crack　shape　(a(0)/c(0))　=　1,　and　it　does　not　change　with　different　initial　crack　depth　ratios　(a(0)/t).　The　established　constitutive　model　can　be　well　used　in　CCG　life　analyses　and　designs　of　high-temperature　structures.