The　long　period　ground　motion　is　a　risk　for　high-rise　building　structures.　For　example,　such　a　lot　of　large　number　of　high-rise　buildings　and　super　high-rise　buildings　in　Chaoyang　District　of　Beijing　will　be　undoubtedly　influenced　by　long　period　ground　motion　in　the　future.　However,　lack　of　the　real　earthquake　records　including　the　long　period　component　has　been　a　restriction　hampering　the　proper　design　of　such　structures　mentioned.　The　response　spectrum　used　in　Chinese　specification　design　is　only　applicable　for　the　structures　with　the　period　less　than　6　seconds.　Hence　the　research　of　the　synthetic　seismic　wave　using　the　artificial　method　is　significant　for　the　seismic　safety　of　high-rise　buildings　and　large-span　structures.　In　this　paper,　through　the　introduction　of　the　synthetic　method　based　on　the　trigonometric　series,　the　method　for　extending　the　period　of　response　spectrum　in　the　synthetic　seismic　wave　is　proposed.　In　the　proposed　method,　the　real　earthquake　records　are　adopted　for　the　phase　information　and　the　time　domain　envelop.　It　gives　simulations　and　comparisons　by　using　the　2011　Great　East　Earthquake　in　Japan.　This　method　considers　the　response　spectrum　of　statistical　information　used　in　Chinese　specification　design　and　reflects　the　non-stationary　natural　seismic　characteristics　to　a　certain　extent.　The　proposed　method　if　of　significance　and　application　value　for　the　research　of　getting　long　period　earthquake　strong　ground　motion　through　the　artificial　composed　method.