Structural　responses　of　a　typical　large-span　hangar　subjected　to　one-,　two-,　and　three-dimensional　(1D,　2D　and　3D)　seismic　excitations,　respectively,　are　analyzed　and　compared　with　each　other,　using　both　response　spectrum　method　and　time-history　analysis　method,　and　then,　the　results　from　the　two　methods　are　compared.　It　shows　that,　for　lateral　displacements　of　the　structure　and　forces　of　the　columns,　the　effect　of　multi-earthquake　inputs　is　mainly　due　to　the　influence　of　the　input　in　the　secondary　horizontal　direction　on　the　above　responses　in　the　corresponding　primary　direction.　When　the　primary　direction　is　along　the　symmetrical　axis　of　the　hangar,　compared　with　1D　inputs,　multi-dimensional　inputs　increase　responses　in　the　main　direction　obviously.　When　it　is　along　the　non-symmetrical　axis,　such　effect　is　not　important;　vertical　input　is　also　negligible　for　them.　Forces　in　different　parts　of　the　roof　are　controlled　by　horizontal　or　vertical　inputs,　respectively,　and,　compared　with　those　from　horizontally　or　vertically　1D　inputs,　responses　from　3D　inputs　are　increased;　The　above　effects　from　time-history　analyses　are　more　significant　than　those　from　response　spectrum　method.　Based　on　these　observations,　some　suggestions　for　seismic　design　of　large-span　hangars　are　then　proposed.