Pumice sand particles present engineering challenges due to their tendency to crush and compress. Although laboratory and field tests can assess their behavior, these methods are often time-consuming and costly. This study investigates the liquefaction behavior of crushable pumice sand using the Discrete Element Method (DEM). In the model, each pumice particle is represented as a sphere that fractures into 14 smaller spheres when a critical contact force is exceeded. Initially, single particle crushing tests are conducted to determine breakage characteristics based on particle size. Subsequently, using the open-source code YADE, three-dimensional loose specimens are prepared and isotropically consolidated under specified confining pressures. These numerical specimens undergo cyclic loading under undrained conditions. The findings indicate that the DEM model successfully replicates experimental results, providing insights into how particle crushing influences cyclic deviator strain. Microscale observations also shed light on the development of force chains within the specimens, enhancing the understanding of pumice sand behavior during cyclic loading.