Sulfated ZrO2-TiO2 mixed oxides with different loading ratios were synthesized using a deposition precipitation approach. All catalysts were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), infrared spectroscopy (IR), energy-dispersive X-ray (EDX) analysis, and transmission electron microscopy (TEM), and the activities for esterification were compared using acetic acid and ethanol as the model reaction. A total of 93.7% acetic acid was converted into ester when 50 wt % ZrO2 loading catalyst was applied at 100 degrees C. The characterizations of original and upgraded Ho-oil via esterification by applying sulfated 50 wt % ZrO2-TiO2 loading ratio catalyst were investigated. After upgrading, fuel properties of pyrolysis oil improved. Acetic acid peak area percentage dropped remarkably from 15.87 to 0.774%, indicating that the properties of Ho-oil were enhanced by SO42-/ZrO2-TiO2 catalytic esterification. Because of ethanol addition, the water content in bio-oil decreased from 40 to 16.9% and the high heating value increased from 8.08 to 22.7 kJ/g.