The aim of this study was to detect the amount of lactic acid (LA) and glycolic acid (GA) in poly(D,L-lactide-co-glycolide) (PLGA) by development a simple HPLC method and to determine the pH of media, which can influence on degradation of PLGA and drug release. Analysis of in vitro degradation behavior of PLGA with two different molecular weights as 8000 and 33,000 g/mol were performed in various media conditions (pH 3.0, 5.0, 7.0, and 9.0 of PBS and distilled water (approx. pH 5.8)). Also, effect of some additives on PLGA degradation was also investigated in pH 7.0 of PBS. GA and LA were easily detected by a simple HPLC method (retention time: 6.5 min and 10.2 min, respectively). The result showed that GA was released larger amount than that of LA considering the initial sample weight of polymers, due to the higher hydrophilic property. In the lower pH of media conditions, the PLGA was faster degraded generally. The presence of various additives, moreover, affected decrease of pH and slight acceleration of LA and GA detection.