Abstract: Precipitation behaviour and effect factors of Z-phase in domestic S30432 steel in supply state and after creeping at different temperatures and stresses were investigated by RD-2 type creep testing,transmission electron microscopy and energy disperse spectroscopy.Results show that only MX phase was observed in S30432 steel in supply state.Cu-rich phase and M23C6 carbide precipitated under the conditions of 650 ℃,170 MPa and 10 712 h.Besides,Z-phase and hybrid MX/Z-phase particles were found under the conditions of 700 ℃,150 MPa and 937 h.Z-phase,whose size increased slowly under the conditions of 700 ℃,150 MPa and 1 944 h,coarsened obviously under the conditions of 700 ℃,100 MPa and 11 832 h.The precipitation of Z-phase could be accelerated by high-temperature and stress.