The fatigue damage characteristic of salt rock is researched based on the acoustic emission (AE) technology by changing the upper limit stress

lower limit stress and loading rate. It is found that the AE count increases slowly with the stress increasing

but for sandstone

the AE count is intensive around the upper limit stress. The fatigue life of salt rock is more dependent on lower limit stress than sandstone. The higher the upper limit stress is

the more the AE count is

and the higher the loading rate is

the damage becomes much earlier. It is found that the AE cumulative curves are in keeping with strain curves which show that they can both show the fatigue damage process of salt rock. In the end

the constant amplitude load is instead by three-level variable amplitude load. The AE count becomes much more in the third level which shows that the variable amplitude load makes more serious fatigue damage in the salt rock than the constant amplitude load does.