Abstract: Both the Loess Plateau(LP)in China and the Mississippi River Valley(MRV)in the USA have serious loess liquefaction disasters triggered by strong earthquakes.However, the liquefaction characteristics in the two regions are different.To analyze the difference in the micro-characteristics including the microstructure, particle size and mineral composition of the undisturbed loess sampled from the LP and the MRV, a series of scanning electron microscope tests, grain size analysis and X-ray diffraction tests are conducted.Besides, the difference in liquefaction behaviors between the loess in the two regions is discussed based on the dynamic triaxial tests.The results show that compared with the LP loess, the MRV loess has more cement, smaller pore sizes, more clay particles and clay minerals, which forms a typical clotted cementation structure among the particles.The porosity, the average pore area and the fractal dimension of the MRV loess are significantly lower than those of the LP loess, causing that the liquefaction resistance of the MRV loess is significantly stronger.The differences of microcharacteristics are the main internal reason for the differences in liquefaction characteristics between the LP loess and the MRV loess.Compared with those of the LP loess, the structural strength, the specific surface area and the hydrophilic mineral content of the MRV loess are larger, which makes the dynamic strain growth be slower and the ability to restrain the development of dynamic pore water pressure be better.