OBJECTIVE： To establish a method for the determination of related substances in Thioctic acid injection. METHODS： HPLC was performed on the column of Agilent Eclipse Plus C18 with mobile phase A of 0.005 mol/L potassium dehydrogenate phosphate solution （adjusted with phosphoric acid to pH 3.0 to 3.1） and B of methanol：aoetonitrile （1 ∶ 1，V/V） （gradient elution） at a flow rate of 1.2 ml/min； detection wavelength was 215 nm， column temperature was 35 ℃， and the injection volume was 20 μl. RESULTS： Under the established chromatographic conditions， thioctic acid with impurities and its degradation products were well separated； the linear range of thioctic acid was 0.828-52.992 μg/ml （r＝0.999 9）； RSDs of precision and stability tests were lower than 3％； recovery of impurity A was 98.45％-105.73％ （RSD＝2.41％，n＝9）； the largest single impurity content in mass fraction was 0.152％-0.189％， the total impurity content in mass fraction was 0.487％-0.516％. CONCLUSIONS： The method is simple， accurate， specific and sensitivity， and can be used to determine the related substances of the Thioctic acid injection.