The current study seeks to develop and validate a high-performance liquid chromatography method for atorvastatin diastereomer separation and analysis. In particular, we wish to identify the many diastereomers in atorvastatin, which can help us to better understand their pharmacological properties and provide significant information for pharmaceutical applications. Atorvastatin was chromatographed on a Chiralcel® OD-RH column and n-hexan-2-propanol (95:05 v/v) as the mobile phase, with an injection volume of 10 µL. The solution was pumped at a continuous flow rate of 1 mL/min, with a detection wavelength of 260 nm. The investigation found two peaks with retention times of 3.23 and 3.85 min, respectively. The resolution, capacity, and selectivity factors obtained were Rs = 1.2, k′1 = 3.50, k′2 = 4.37, and α = 1.24.