In this study, we investigated the preparation of ferulic acid, one of potential antioxidantswhich is widely used in the pharmaceutical industry, and cosmetics, from the hydrolysis ofgamma oryzanol (γ-oryzanol), compounds containing by-product of rice bran oilprocessing. In alkaline solution using co-solvent, γ-oryzanol hydrolysis reaction has beenstudied and examined in terms of the different rates of alkaline catalysts, temperature, andultrasonic (20 kHz). We investigated suitable analysis conditions to simultaneouslyanalyze the product of the γ-oryzanol hydrolysis reaction, optimized hydrolysis conditionsto obtain high efficiency. In heat treatment condition, with the intial concentration of γ-oryzanol of 6 mg/mL, and KOH/ γ-oryzanol ratio is 20:1 (wt/wt), the reaction at 75 oC gotthe efficiency of 83.3%. Meanwhile, at 60 oC using the ultrasonic assistance (20 kHz, 180W), the efficiency was reached up to 93.3% in just 2.5 hours. The aim of this work is tomake a basic data for the ferulic acid production research process from soapstock, abyproduct that has high γ-oryzanol concentration.Keywords: ferulic acid, γ-oryzanol, ultrasonic, hydrolysis reaction, co-solvent