Abstract: The 2023 Jishishan M6.2 earthquake induced the liquefaction flow slip of loess in Zhongchuan Township. In order to reveal its low-angle long-distance slip mechanism, based on the dynamic triaxial test and microstructure analysis of undisturbed saturated loess samples, the effects of confining pressure and dynamic stress amplitude on the changes of dynamic strain and pore water pressure were studied. The results show that the development of dynamic strain is characterized by three stages. The change of pore pressure is controlled by dynamic stress and confining pressure. Under low dynamic stress, the pore pressure increases slowly, and the liquefaction critical value is high. Under high dynamic stress, the pore pressure increases rapidly, and the liquefaction critical value decreases. The dynamic strain and pore pressure peak increase synchronously in the early stage, and lose synchronization in the later stage. The normalized analysis shows that the two have dynamic correlation. Microscopically, liquefaction destroys the overhead pore structure and promotes the pore connectivity to form a seepage channel. Quantitative analysis shows that the pore complexity increases and the shape regularity decreases. Dynamic load causes structural collapse, seepage enhancement, pore pressure rise, and effective stress loss, synergistic strain development, and ultimately triggers saturated loess liquefaction.