This study was conducted to examine the effects of Jeot-kal and chitosan on the physicochemical characteristics and hardness during onion Kimchi fermentation. The onion Kimchi was stored at 4±1℃, for 42 days. The study results were as follows. The pH of control onion Kimchi and the experimental groups was in the range 5.30~5.80. The pH of the experimental groups slowly decreased during the fermentation. The total acidity of the four kinds of onion Kimchi was increased. The reducing sugar content was maximized at 4 days of fermentation, after which it decreased gradually as the fermentation processed. The ascorbic acid content of control onion Kimchi and the experimental groups was increased rapidly at 21 days and then decreased. The hardness of onion Kimchi measured instrumentally was higher in onion Kimchi treated with the salt-fermented Toha jeot juice than in control onion Kimchi.