In this study, a hydrothermal pretreatment of an empty fruit bunch (EFB) was carried out to improve the fuel properties. The possibility of reusing the hydrolysate generated from this process was examined using three different adsorbents (XAD 4, XAD 16 resin, and activated carbon). The degradation rate was 19.46% during the hydrothermal pretreatment, which increased to 20.05-26.77% by the reuse of hydrolysate depending on the adsorbent. The inorganic compound and degradation products contained in the hydrolysate were removed by the adsorbent. In particular, the total phenolic compounds were removed effectively (3.9-49.6%) by activated carbon. The inorganic compounds were removed by activated carbon with a 2.8-12.4% removal rate. The heating value was increased slightly by the reuse of hydrolysate. Finally, the fuel properties were improved by removing the inorganic compounds and improving the heating value.