This　paper　presents　a　new　method　that　combines　PCA　with　HSI　to　differentiate　and　extract　construction　shadows　from　high　resolution　remote　sensing　images　and　then　calculates　each　block　floor　area　ratio　by　using　regression　analysis.　The　proposed　method　reduces　the　complexity　and　instability　when　extracting　floor　area　ratios　using　the　traditional　method.　Taking　downtown　Fuzhou　as　an　example,　we　extracted　the　construction　shadow　and　floor　area　ratio　by　the　new　method,　to　compare　and　validate　it　against　the　traditional　method.　The　results　show　that　the　shadow　index　from　the　new　method　is　more　reliable　and　precise　than　results　obtained　from　the　traditional　approach.