Abstract: This　paper 　presents 　a　new　method　that 　combines　PCA　with　HSI　to　differentiate 　and　extract construction　shadows 　from　hi gh　resolution 　remote 　sensing　images 　and　then　calculates 　each　block 　floorarea 　ratio　by　using　re gression 　anal ysis．The 　proposed　method　reduces 　the 　complexit y　and 　instabilit y 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　methodto 　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．