Since　the　discovery　of　the　long　period　component　in　the　strong　ground　motion,　it　is　aware　that　the　influence　of　long　period　components　on　the　structures　with　long　periods　cannot　be　ignored.　In　current　design　codes,　the　seismic　design　for　buildings　with　long　periods　is　conservative,　and　the　values　of　spectrum　are　artificially　magnified　for　the　specific　frequency　range　of　ground　motions　and　specific　site　conditions,　which　conflicts　with　the　actual　records　of　ground　motions.　In　view　of　the　deficiency　in　current　design　codes,　a　modified　method　is　proposed　for　the　design　spectra　in　the　range　of　5Tg　to　6s,　according　to　the　seismic　input　spectra　of　the　total　energy　and　the　instantaneous　energy　for　a　single　degree　of　freedom　system.　Based　on　the　actual　records　of　ground　motions　with　long　period　components　which　possess　the　characteristic　of　velocity　pulse,　the　proposed　method　is　evaluated,　the　modified　acceleration　spectrum　is　obtained,　and　the　pseudo-velocity　spectrum　and　the　displacement　spectrum　associated　with　the　acceleration　spectrum　can　also　be　attained.　The　proposed　method　can　reflect　the　characteristics　of　the　seismic　input　spectra　for　the　total　input　energy　and　the　instantaneous　input　energy,　which　shall　be　of　theoretical　importance　and　practical　application　for　the　seismic　design　of　structures.　©　2018,　Editorial　Office　of　China　Civil　Engineering　Journal.　All　right　reserved.