Abstract: Creep tests were conducted on 25Cr35Ni heat-resistant steel at different temperatures T and different stresses σ. The temperature and time at different creep strains were normalized by introducing parameter P. The variation of (P,σ) data point with creep strain was analyzed. Parameter Z_c was proposed to analyze the dispersion degree of data and to predict the creep rupture life with experimental data at creep strain of 5.0%. The results show that with increasing creep strain, the σ-P curve became close to the fracture curve; the value of Z_c increased rapidly and then became stable; the deviation between (P,σ) data point and the corresponding fitting curve decreased. The predicted rupture lives on basis of Z_c parameter method were close to the experimental rupture lives; the dispersion degree was relatively small.