OBJECTIVE:To establish a HPLC method for determination of anthraquinone free derivatives from Chinese herbal in dog serum METHODS:With Hypersil BDS C18 column,the mobile phase was methanol-0 5% acetic acid(80∶20) The sample was extracted with methanol and dried at room temperature The residue was reconstituted by methanol and analyzed at 430nm RESULTS:The five components can be separated well The linear ranges were Aloe-emodin(0 15～6 0?g/ml,r=0 9 996) Rhein(0 14～5 6?g/ml,r=0 9 982);Emodin(0 13～5 2?g/ml,r=0 9 990);Chrysophanol(0 2～8 0?g/ml,r=0 9 991);Physcion(0 1～4 0?g/ml,r=0 9 994) CONCLUSION:This method can provide the basis for vivo analysis of anthraquinone free derivatives and bioavailability study of Rheum palmatum preparations