A high performance liquid chromatog. (HPLC) method for determination of the related substances of atorvastatin intermediate L1 was established.The chromatog. separation was performed on Agilent Poroshell EC-C18 column (100 mm×4.6 mm, 2.7 μm) with the mobile phase consisting of H2O: ACN: THF: MeOH (36: 8.4: 29: 26.6).The flow rate was 0.7 mL·min-1, the detection wavelength was 246 nm and the column temperature was 30°C.The method achieved good separation between L1 and its related impurities including L1-defluorination, L1-R, S, and L1-diamination.The linear range was 0.124 1-1.488 0 μg·mL-1 (R2=0.999 5, n=7) 0.386 6-3.093 0 μg·mL-1 (R2=1, n=6), 0.357 1-2.856 0 μg·mL-1 (R2=0.999 0, n=6), and 0.187 3-1.498 0 μg·mL-1 (R2=0.999 3, n=6) for L1-diamination, L1-defluorination, L1-R, S and L1-difluorination, resp.The specifications of each impurity all reached the LOQ.L1 separates well with the impurities.The method is accurate and reliable.