The　multi-dimensional　seismic　response　of　a　single-span　hangar　was　studied　by　response　spectrum　analysis　method.　The　lateral　displacements　of　the　structure,　forces　of　its　supporting　columns　and　its　roof　structure　were　calculated　and　compared　with　each　other　for　cases　of　one-,　two-　and　three-dimensional　(1D,　2D　and　3D)　seismic　inputs.　The　results　show　that,　compared　with　the　case　of　1D　earthquake　input,　the　effects　of　horizontally　2D　earthquake　inputs　on　the　internal　forces　and　displacements　of　its　supporting　columns　in　the　primary　direction　of　input　are　obvious　when　it　is　along　the　symmetrical　axis　of　the　hangar　and　their　effects　in　the　secondary　direction　of　input　are　even　more　important　which　results　in　great　increases　of　the　internal　forces　and　displacements　in　that　direction.　The　vertical　seismic　input　has　almost　no　effect　on　the　internal　forces　and　displacements　of　columns.　The　internal　forces　in　different　parts　of　the　roof　structure　are　controlled　by　horizontal　or　vertical　inputs,　respectively,　and,　compared　with　those　from　horizontally　or　vertically　1D　inputs,　the　responses　from　3D　inputs　are　increased　and　the　effects　should　be　considered　in　seismic　design.