The internal stress of a lump coke in a coke oven chamber is analyzed using a creep model, which can represent a deformation behavior of the lump coke. The thermal stress analysis, which has been previously developed by authors to estimate the stress distribution within the lump coke in the laboratory scale oven, is improved with considering the creep characteristics of the plastic and semi-coke layers, dilatation of the plastic layer and the pyrolytic reaction fraction dependence of thermophysical properties. The effects of the above-mentioned models on the stress distribution and deformation behavior within the lump coke are discussed in this study. The calculated stress distribution and deformation behavior within the lump coke lead to the following conclusion: 1) The pyrolytic reaction fraction dependence of the thermophysical properties influences on the results of the heat transfer within the lump coke and the heating rate at the region near the coke oven center is estimated to be higher than one calculated with the properties which are measured in the constant heating rate condition. 2) The y-directional tensile stress at the center of the lump coke, which is calculated with the creep analysis, is half of the one of the elastic analysis. 3) The clearance which is defined as a distance between heated wall and lump coke is smaller because of considering the dilatation of the plastic layer. 4) The model used in this study can more accurately predict the formation/propagation of transverse fissure within the lump coke. Thus the creep model would be an effective tool to investigate the coking process.