Under the influences of rainfall infiltration and underground runoff，the rock foundation of inland port undergoes the dry-wet cycle，and the bearing capacity of the foundation gradually decreases with time.Taking siltstone as the research object，we carry out nuclear magnetic resonance (NMR) and uniaxial compression tests under five dry-wet cycle conditions.Based on the geometric damage and energy damage，we build two damage evolution equations combining with the change law of rock pore volume and elastic modulus，and analyze the dry-wet cycle damage evolution mechanism of siltstone.The results show that the T2 spectrum of siltstone shows three peaks，corresponding to smaller，small and large pores respectively，and the structural pores of siltstone are smaller and small pores.With the strengthening of dry-wet cycle，the total area of T2 spectrum peak and porosity show a power function increasing law，and the number of rock pores increases gradually.The dry-wet cycle promotes the attenuation of the peak strength and elastic modulus.When the number of cycles reaches 16，the attenuation amplitude gradually flattens.