In order to solve the stability problem caused by low strength and significant creep characteristics of soft rock in slope engineering of open-pit coal mines，the creep deformation characteristics and constitutive model of soft rock were studied. By taking the mudstone of an open-pit coal mine in eastern Inner Mongolia as the research object，based on the results of the triaxial creep test and the analysis of the traditional Burgers creep model，a new non-linear five-element creep damage model was established by introducing a strain-triggered non-linear dashpot. According to the principle of least squares，the parameters of the improved creep damage model were identified. The results show that the improved Burgers creep damage model has a fitting coefficient with the experimental data，which can fully describe the creep deformation characteristics of mudstone in the whole stage，especially in the accelerated creep damage stage. The fitting degree of the improved creep damage model is obviously better than that of the traditional Burgers creep model.

soft rock  /  non-linear  /  creep model  /  damage  /  dashpot