An　analytical　solution　to　spectral　density　function　of　across-wind　load　fluctuation　acting　on　the　structure　flank　is　presented　from　the　original　fluid　movement　equation　in　turbulence　theory　under　certain　assumptions.　The　spectral　density　function　of　wind　load　fluctuation　could　be　derived　from　the　CFD　wind　average　velocity　and　fluctuating　velocity　distribution　according　to　Taylor＇s　Frozen　Assumption　of　turbulence.　All　the　T-M　contributions　have　been　taken　into　account　in　the　analysis　process.　This　could　be　regarded　as　an　effective　verification　of　the　datum　from　wind　tunnel　test　and　datum　from　full　scale　observation.　The　analysis　of　structure　dynamic　response　induced　by　this　kind　of　wind　load　fluctuation　could　then　be　achieved　without　the　expensive　wind　tunnel　test.