Based on the parameter changes of strong collapsible loess in Xi’an before and after humidification, a finite element model of pile group was established, and the pile group effect and negative skin friction characteristics of pile foundation after loess collapse caused by the rise of groundwater table were analyzed. The results show that the effect of pile diameter change on negative skin friction is not obvious, and with the increase of pile diameter, negative skin friction has a weak tendency to decrease. The pile group effection has a significant weakening effect on the negative skin friction, and the pile group effect weakens as the pile spacing increases, and when the pile spacing exceeds six times the pile diameter, this effect is minimal. When the pile spacing is six times the diameter, the total negative skin friction of the edge pile in the group pile is very close to that of the single pile. The axial force have a strong correlation with the friction resistance of the pile side, from the top of the pile downward, the friction resistance changes from negative to positive at the neutral point, while the axial force of the pile body has a vertex at the neutral point. In addition, due to the weight of the cushion cap, not only the neutral surface depth ratio is reduced, but also the axial force of the pile group increases.