Base　on　the　analysis　of　structural　seismic　reliability＇s　traditional　calculation　method,　there　are　something　was　found　Because　of　the　rough　correlation　between　earthquake　ground　acceleration　and　intensity　in　the　traditional　method,　the　seismic　reliability　calculation　results　were　far　from　the　earthquake　damage　facts.　In　this　paper,　an　improvement　which　is　the　peak　acceleration　distribution＇s　discreteness　relates　with　probability　of　seismic　intensity　was　adopted,　and　an　a　amendatory　seismic　reliability　formula　was　proposed　which　based　on　the　peak　ground　motion　acceleration　distribution　corresponding　to　the　probability　of　seismic　intensity.　This　method　was　also　used　for　analyzed　the　seismic　safety　performance　of　a　simply　supported　beam　bridge.　©2010　IEEE.