When the slope foundation soil is underconsolidated,not only the influence of the negative skin friction of the pile foundation in the slope area,but also the lateral extrusion on the pile foundation due to slope soil should be considered.But no specific provisions for the latter issue are recommended in the current code and manuals.To solve this problem,combining the actual engineering design,we analyze the interaction of the underconsolidated soil foundation slope and pile foundation by using the soft soil model and the Mohr-Coulomb model based on geotechnical engineering finite element simulation software PLAXIS.The result shows that the calculation of slope stability tends to be safe without considering the effect of pile foundation;however the calculation of pile foundation tends to be unsafe without considering the influence of the soil consolidation deformation of the slope.It is suggested that the design of pile foundation should consider the effect of lateral soil pressure on the pile due to the slope deformation,especially when the interaction between the under-consolidated foundation slope and the pile foundation is complex,more attention should be paid to the pile design,for the consolidation settlement of slope soil has obvious influence on pile foundation.