Abstract: Using the high temperature fatigue testing system with scanning electron microscope, we observed the influence of temperature's change on limestone'smicrostructure in real time, effectively avoided the influence of thereversible process of rock's heat inflating, which is influenced by thehistory of temperature and theinfluence of the difference of its properties during heating and aftercooling. And it was also found that the samples have not created hotcracks in the heating process, but have created lot of tiny cracks inthe cooling process. The experimental results indicate that the rock's microstructurechanges at heating process and cooling process are different. Thismay due to the residual stress produced in the cooling process of limestone.