Granular materials are prone to liquefaction failure under various undrained loading conditions, while the liquefaction mechanisms of such materials remain insufficiently understood. Based on complex network theory, the topological evolution mechanisms of strong contact networks during the liquefaction process of granular materials were investigated. Quasi-static loading-unloading tests under different confining pressures and stress levels were carried out using DEM (discrete element method), and the macroscopic responses were analyzed. Several representative state points during the loading-unloading process up to liquefaction were selected, and the topological evolution characteristics of the strong contact networks were examined. The results indicate that irreversible macroscopic and microscopic responses were observed in granular specimens after experiencing loading-unloading histories, accompanied by a reduction in undrained strength. During cyclic loading and unloading, as the selected stress level approaches the peak stress, fewer cycles are required for the specimens to reach the liquefaction state, and the spacing of the stress-strain hysteresis loops becomes larger. In the non-liquefied state, the number of particles in the largest cluster, the relative size of the largest cluster, and the network diameter of the largest cluster in the strong contact system exhibit consistent evolution trends with increasing threshold values. However, in the liquefied state, the force transmission structure was completely destroyed, and the percolation of contact forces in the strong contact network could not be established even at relatively small threshold values.