In　the　seismic　time-history　analysis　of　spatial　structures　under　one-dimensional　and　three-dimensional　seismic　excitation,　significant　error　will　be　induced　under　certain　seismic　records　if　the　Rayleigh　damping　coefficients　are　computed　by　the　traditional　two　reference　modes　(TRM)　method.　To　solve　the　problem,　with　the　modal　maximum　strain　energy　as　weight,　a　multi-mode　based　weighted　least　square　(WLS)　method　is　proposed　to　compute　the　Rayleigh　damping　coefficients.　A　formula　for　the　Rayleigh　damping　coefficients　obtained　by　the　new　method　is　presented.　In　the　case　of　one-dimensional　and　three-dimensional　seismic　excitation,　with　the　seismic　responses　under　benchmark　damping　ratio,　two　double　layer　cylindrical　latticed　shells　are　taken　as　examples　respectively　to　compare　the　errors　of　the　new　method　with　those　of　the　traditional　two　reference　modes　method.　The　results　show　that　the　new　method　is　more　reasonable　than　the　traditional　TRM　method　for　spatial　structures,　and　it　retains　the　simplicity　and　convenience　of　the　Rayleigh　damping　theory.