Abstract: By setting a group pile in a free field, changing the distance between piles, the series numerical simulation test was completed for the liquefaction in a pile-foundation non-free field by using FLAC3D. Studied the influence on liquefaction distribution features of the pile-foundation non-free field, and revealed the anti-liquefaction nature of a group-pile foundation. Experiment showed that: the non-free field liquefaction distribution approaches non-uniform in the horizontal direction, the pore-water pressure distribution shifted, the contour of pore pressure presents the fluctuation shape, nearby the structure forms the low pressure region, and forms the high pressure region several meters far to the structure. Contrast with the free liquefaction field, the excess pore pressure ratio in a low pressure region reduces obviously, approximately 20%, and the anti-liquefaction effect on top soil of a pile foundation was very limited. The excess pore pressure ratio in a high pressure region is higher than the free field. The group pile suppressed the vicinity soil liquefaction, and the piles strengthened the liquefaction in distant place soil. The bigger the pile rigidity is, the bigger the inhibition range is, and the bigger invigoration effect to the distant place liquefaction is also. The smaller the pile rigidity is, the smaller inhibition range is, and the smaller the invigoration effect to the distant place liquefaction is also. At same distance between piles, when the pile diameter is bigger, the excess pore pressure ratio in the field between piles is lower. Researching results will provide a theoretical and experimental basis for the anti-liquefaction design of underground pipes through the liquefied soil layer.