Time-history　response　analyses　of　a　long-span　hangar　based　on　site-class　IV　are　conducted　under　different　multi-dimensional　earthquake　inputs　for　the　seismic　fortification　intensity　of　7　to　study　its　seismic　response　and　requirements　for　seismic　design.　The　lateral　displacements　of　the　structure,　internal　forces　of　its　supporting　columns　and　the　members　of　the　roof　in　the　cases　of　one-,　two-　and　three-dimensional　seismic　inputs　were　compared,　respectively.　The　results　show　that,　the　dynamic　analyses　of　three-dimensional　seismic　motions,　different　directions　of　the　inputs,　i.e.,　positive　or　negative　along　the　axis,　result　in　asymmetric　global　torsions　of　the　structure.　Some　displacements　and　internal　forces　of　the　columns　are　increased　significantly　with　multi-dimensional　earthquake　inputs,　compared　with　the　one-dimensional　ones.　Seismic　inputs　in　horizontal　and　vertical　directions　have　different　effects　on　different　parts　of　the　roof　structure,　dominating　member　forces　of　the　space　truss　and　the　truss　at　the　gate,　respectively.　Member　forces　of　the　roof　from　three-dimensional　inputs　are,　as　a　whole,　significantly　greater　than　those　only　from　inputs　in　horizontal　or　vertical　directions,　and　a　large　portion　of　members　has　large　seismic　coefficients　of　member　force.　The　distribution　of　roof　members　with　large　values　of　seismic　coefficients　was　also　illustrated.　Therefore,　it　is　recommended　that,　for　long-span　hangars　in　such　conditions,　seismic　verification　is　needed,　in　which　the　effects　of　three-dimensional　earthquake　should　be　taken　into　account.