Considering　a　circular　tunnel　embedded　in　saturated　soil,　the　amplification　of　site　ground　motion　due　to　the　tunnel　is　studied　by　a　2.5D　finite　element-boundary　element　coupling　method.　It　is　assumed　that　seismic　waves　are　incident　at　an　arbitrary　angle　from　bedrock,　and　the　incident　direction　is　described　by　a　horizontal　angle　θh　and　a　vertical　angle　θv.　A　parametric　investigation　on　the　effects　of　the　incident　angle　of　seismic　waves　on　ground　acceleration　responses　is　conducted.It　is　shown　that　the　amplification　factors　of　the　ground　accelerations　for　the　oblique　incidence　case　are　much　larger　than　those　for　the　vertical　incidence　case.　Moreover,　the　incident　angle　also　has　a　big　influence　on　the　acceleration　response　spectra,　in　terms　of　the　amplitude,　distribution　pattern　and　predominant　period,　and　the　influence　is　more　pronounced　for　the　vertical　acceleration　responses.　It　is　also　shown　that,　for　the　numerical　example　in　this　study,　when　θhv＞　30°,　the　ratios　of　the　amplitudes　of　the　vertical　accelerations　to　those　of　the　horizontal　accelerations　can　be　larger　than　0.65　which　is　recommended　by　the　code　for　seismic　design,　and　the　amplitudes　of　the　response　spectra　for　the　vertical　accelerations　may　be　larger　than　those　for　the　horizontal　accelerations.　©　2020,　Editorial　Office　of　China　Civil　Engineering　Journal.　All　right　reserved.