In　recent　years,　the　urban　infrastructure　construction　in　China　has　been　constantly　developing.　The　pile　foundation　is　a　common　form　of　foundation　in　infrastructure　construction.　The　calculation　of　the　capacity　of　a　pile　foundation　is　an　important　subject　in　the　foundation　design.　Based　on　the　Vesic　expansion　theory,　the　actual　stress　state　of　the　soil　on　the　pile　side　under　horizontal　loading　is　presented.　A　calculation　method　of　the　soil　resistance　on　the　pile　side　in　the　form　of　stress　increment　is　derived,　and　the　mechanical　method　of　the　horizontal　capacity　of　the　pile　foundation　considering　the　pile-soil　interaction　is　proposed.　The　corresponding　analysis　program　was　compiled　based　on　MATLAB　software　and　the　validity　of　the　proposed　calculation　method　was　verified　by　a　comparison　with　experimental　results.　The　effects　of　the　load　and　the　pile　diameter　on　the　mechanical　behavior　of　the　pile-soil　interaction　system　was　analyzed　based　on　the　proposed　mechanical　model　for　the　horizontal　bearing　capacity　of　pile　foundation.　Copyright　©2021　Engineering　Mechanics.　All　rights　reserved.