With the widespread application of variable cross-section CFG piles in the engineering field,studying their me-chanical properties has significant theoretical and practical implications.This paper aims to explore the impact of the lower pile diameter of variable cross-section CFG piles on their mechanical properties,particularly the mechanical response of variable cross-section CFG piles under different pile diameters.Using the ABAQUS finite element software,an overall fi-nite element model of the variable cross-section CFG pile-soil system was established.For variable cross-section CFG piles with diameters of 1.2 m,1.4 m,and 1.6 m,the mechanical responses under the same uplift load,horizontal load,and downward load conditions were analyzed.The research results show that as the smaller pile diameter increases,the maxi-mum stress and maximum displacement of the variable cross-section CFG pile gradually decrease,and the stress concentra-tion mainly occurs in the upper larger pile area.This study provides a theoretical basis for the design and construction of variable cross-section CFG piles and helps improve their bearing capacity and stability under complex geological condi-tions,having significant engineering application value.