Hawthorn stones, a waste biomass, were subjected to supercritical ethanol extraction to obtain bio-oils. Optimization of the extraction parameters was performed according to the Box-Behnken design to estimate the effects of extraction temperature, extraction time, and biomass concentration on the yields of the bio-oil and the conversion of the biomass. High correlation coefficients (R-2) were obtained. The values of R-2 were 0.90 and 0.98% for bio-oil and biomass conversion, respectively. The validity of the model used in this procedure was indicated by the consistent matching of predicted values with the experimental values. The experimental results demonstrated that the optimized conditions fell within the range of the experimental design.