To　improve　the　computing　effectiveness　of　huge　spatial　structures　for　earthquake　analysis,　the　load-dependent　Ritz　vector　is　introduced　into　the　mode　superposition　or　the　mode　transient　analysis　method.　The　computing　time　of　the　direct　integration　method　and　the　mode　superposition　method　by　using　characteristic　eigen　vectors　has　been　decreased　by　several　percent.　The　computing　accuracy　can　satisfy　the　engineering　demand　easily.　This　method　can　also　be　used　in　the　wind　vibration　analysis,　comfort　analysis　and　other　dynamic　analysis　for　the　structure.