Onion and garlic extracts, and their 6 microfiltrates separated through molecular weight cut-off were introduced to the cell viability of fish gill and antibacterial activity trials in this study. The onion extract and its microfiltrates revealed inhibitory effect on cell viability and no effect when they were diluted to 2000-fold dilution. The garlic extract and its 6 microfiltrates were no inhibitory effect on cell viability, and when their concentrations up to 2-6 g/ml the cell viability increased significantly. Onion and garlic extracts, and their 6 microfiltrates exhibited antagonistic activities against Photobacterium damselae subsp. piscicida and Streptococcus iniae.