The analytical methods for the standardization of α-mangostin are needed to set up a routine of a validated method for quality control of α-mangostin from Garcinia mangostana L. using HPLC methods. This study was aimed to validate the analytical method of High-Performance Liquid Chromatography (HPLC) for α-mangostin analysis with Photodiode Array (PDA). The analysis was conducted by HPLC with octadecyl silanol column, methanol and acetic acid 1% as a mobile phase and PDA detection at 243 nm. The coefficient correlation of analytical method was was 0.9999, the variation was less than 2%, LOD was 0.671 ppm, and LOQ was 2.174 ppm. The level of α-mangostin in mangosteen pericarp extract from Tasikmalaya was 8.56 ± 0.003%. The analytical method was met the validation criteria. The PDA sensitivity was 68.28% higher than UV-Vis detector.