In order to take full advantage of Incoloy800H alloy, the creep behavior of Incoloy800H alloy tubes at temperatures ranging from 600℃to 1050℃ was investigated based on creep character-temperature parameter models. The reliability equations of steady creep rate, rupture time and initiation time of tertiary creep were obtained by multiple linear regression. The effective relationships among allowable stress, service temperature and reliability were established. The results demonstrate that the creep reliability equations make the prediction for creep behavior of Incoloy800H alloy tubes more accurately. The long-term creep data are completely located in the 0.997 confidence band of predicted results by corresponding reliability equations. In comparison with recommended allowable stresses by ASME, the creep reliability equations can provide more reasonable evaluated results.