Abstract: The significant influence of loading and unloading history on creep deformation indicates that the cyclic stress environment in underground engineering (such as excavation, backfilling, and unloading) can alter the long-term stability of salt rock. Based on this, creep tests of salt rock under stepped loading and unloading at the same stress level were conducted to investigate the effects of different loading and unloading histories on the creep behaviour of salt rock. By introducing a state variable that characterizes the degree of rock hardening, a creep constitutive model for salt rock was established to account for the influence of loading and unloading history, enabling more accurate characterization and prediction of salt rock deformation behaviour. The creep rates under ascending and descending stress gradients exhibit significant differences due to the influence of loading and unloading history. The new creep constitutive model based on state variables shows a high degree of agreement between the fitted creep deformation curves under different loading paths and the test curves, providing a good prediction of the historical effects on the creep behaviour of salt rock. In addition, the plastic deformation during loading is only related to the stress state before and after loading, and is independent of the loading path, loading and unloading rate, and loading and unloading time. Parameters k, m, and c influence the model by affecting the state variable. Parameter a affects the model by influencing steady-state creep deformation, while parameter b affects the model by influencing variable creep strain. Parameter n characterizes the sensitivity of creep deformation to stress, while also affecting both decay-rate and steady-state creep deformation.