Central composite design along with response surface methodology (RSM) was applied to improve the fermentation process in onion (Allium cepa) wine production. The effects of different fermentation parameters (time, temperature, and initial sugar content) were found to be significant with respect to the physicochemical and sensory properties of wine. The maximum score for the alcoholic content was obtained at 29.27℃ fermentation temperature, 103.43 h fermentation time, and 27.52 °Brix initial sugar content. The maximum score for overall palatability was obtained at 39.27℃ fermentation temperature, 57.28 h fermentation time, and 22.14 °Brix initial sugar content. The coefficients of determination (R2) were 0.9620 and 0.9060 for alcoholic content and overall palatability, respectively. The ranges of the optimum fermentation conditions (28~32℃, 80~90 hr, and 20~25 °Brix) were obtained by superimposing the response surfaces with regard to the alcoholic content and overall palatability of onion wine.