OBJECTIVE： To establish a method for the simultaneous content determination 5 anthraquinones of rhei radix-coptidis rhizoma， and optimize its best mass ratio. METHODS： HPLC was performed on the column of Zorbax SB-C18 （250 mm×4.6 mm， 5 μm） with mobile phase of acetonitrile-0.05 mol/L potassium dihydrogen phosphate （48 ∶ 52，   V/V， adding sodium dodecyl sulfate 0.4 g per 100 mL， pH value was adjusted to 4.0）； detection wavelength was 254 nm； flow rate was 1 mL/min； column temperature was 25 ℃； and injection volume was 10 μL. When mass ratio of rhei radix-coptidis rhizoma was 1 ∶ 1， 1 ∶ 2， 2 ∶ 1， 2 ∶ 3， 3 ∶ 2， the contents of aloe emodin， rhein， emodin， chrysophanol and emodin ether were investigated. RESULTS： The aloe emodin， rhein， emodin， chrysophanol and emodin ether showed good linear relationship with peak area in the range of 0.652-3.081， 0.704-3.422， 1.280-6.197， 0.633-0.324， 1.326-5.954 μg （r≥0.999 7）； RSDs of precision， stability， reproducibility tests were lower than 2.0％ （n＝6）； and average recovery was 98.92％-100.37％ （RSD≤2.26％， n＝6）. When mass ratio was 2 ∶ 1， the total contents of 5 ingredients were the highest. CONCLUSIONS： The method has good precision， stability， reproducibility， and can be used for the quality verification of rhei radix-coptidis rhizoma under different compatibilities. The best mass ratio of rhei radix-coptidis rhizoma is 2 ∶ 1.