To investigate the effect of onion on kimchi fermentation, the changes on the pH, total acidity and total sugar content of kimchi with the addition of different amouts (5%, 10% and 15%) of onion were measured and the odor and taste evaluation was conducted during fermentation at $14^{circ}C$ for 20 days. As the fermentation period increased, fermentation rate of kimchi contained onion was higher in 5% onion and was lower in 10% and 15% onion than that of control kimchi, sensory evaluation score of onion kimchi was lower in 5% onion and higher in 10% and 15% onion than that of control kimchi.