Attempts have been made in this study to recover reducing sugar from coconut pith by pretreating the pith with a mineral acid (sulphuric acid) and an organic acid (oxalic acid). Pretreatment was carried out in a high pressure batch reactor (HPBR). Biomass loading, reaction time, temperature and acid concentration were chosen as operating parameters. Response Surface Method (RSM) was used to determine the optimum condition. When 87 mg / ml of biomass was treated with 7.56% (w/w) oxalic acid at 134 circ C for 35 min, 62% reducing sugar was recovered. On the other hand, a recovery of 62% reducing sugar was observed when 79 mg/ml of biomass loading with 2.01% (w/w) sulphuric acid was treated at 127 circ C for 50 min. In summary, considering the acid concentration, it was found that pretreatment of oxalic acid is effective for recovering reducing sugars from coconut pith In addition, 33% of glucose yield was observed in the enzymatic saccharification of the oxalic acid pretreated solids in 96 h. In order to investigate morphological changes before and after pretreatment, pith was examined using FTIR, XRD, SEM. © 2018 IEEE.