OBJECTIVE：To establish a method for determination of dextran70 in Compound dextran70 eye drop. METHODS： HPLC-RID was performed on the column of Phenomenex PolySep-GFC-P 4000 with the mobile phase of 0.7％ Na2SO4 solution. The flow rate was 0.5 ml/min，column temperature was 35 ℃ and injection volume was 50 μl，and the inner temperature of refractive index detector was 40 ℃. RESULTS：The linear range of dextran70 was 0.1-5.0 mg/ml（r＝0.999 5）；RSDs of precision，stability and reproducibility tests were lower than 2％ ；average recovery was 97.45％ -101.76％（RSD＝0.57％ ，n＝9）. CONCLUSIONS： The method is simple，fast and reliable with high separation and short analysis time，and can be used for the content determination of dextran70 in Compound dextran70 eye drop.