OBJECTIVE： To study the effects of slice and segment on the extraction amount of polysaccharides， bibenzyl compounds and dendrophenol from Dendrobium denneanum， and to compare the advantages and disadvantages of D. denneanum slice and segment. METHODS： The steamed D. denneanum was cut into segment with length of 10 mm and slice with thickness of 4 mm， and then dried at 60 ℃. Then D. denneanum slice （segment） decocte 60， 90， 120 min and warm-soak 60， 90 min， UV spectrophotometry was used to determine the extraction amount of polysaccharides and bibenzyl compounds from it. HPLC method was used to determine the extraction amount of dendrophenol from D. denneanum slice （segment）， and calculate the extraction rate of it separately. RESULTS： Compared with D. denneanum segment， the extraction amount of polysaccharides and bibenzyl compounds in D. denneanum slice were increased by 0.06-0.17 mg/g and 0.08-0.11 mg/g during decocting， and the extraction rate of dendrophenol was increased by 37.5％. During the warm-soaking process， compared with D. denneanum segment， extraction amount of polysaccharides and bibenzyl compounds in D. denneanum slice were increased by 0.33-0.58 mg/g and 0.17-0.28 mg/g， respectively. Compared with D. denneanum segment the extraction rates of water-soluble extracts and alcohol-soluble extracts in D. denneanum slice were increased by 2.89％ and 0.98％， respectively. CONCLUSIONS： D. denneanum slice is superior to D. denneanum segment， which provides reference for changing segment into slice about the cutting of D. denneanum in Chinese Pharmacopeia.