Abstract: Natural liquefiable sandy ground and liquefiable sandy ground improved by gravel piles and soil cement piles under earthquake action are numerically simulated by three-dimensional finite difference program “FLAC^3D” (Fast Lagrangian analysis of continua), and anti-liquefaction characteristics of gravel piles and soil-cement piles in improving the liquefiable sandy ground are studied. The analysis shows that the gravel piles have remarkable effect to resist liquefaction, while the cement-soil piles have limit effect to resist liquefaction. It is also confirmed that the resisting liquefaction effects and the drainage effects of pile-soil are directly correlative .