Skipjack was used as raw material in this study,the differences of heat-mass transfer and quality changes between fast-freezing( 1. 40 cm / h) and slow-freezing( 0. 46 cm / h) in cold brine onboard was invesigated. The results revealed that the freezing time needed for fast-freezing and slow-freezing were 9 hours and 24 hours,respectively. The salt uptake of skipjack by fast-freezing process was significantly slower( P < 0. 05) than slow-freezing. During early freezing stage and storage time,TVB-N value of skipjack by fast-freezing increased slowly and failed to exceed 20 mg /100g after 28 days of storage. Meanwhile,Changes of pH value,TBA value,metmyoglobin percentage of skipjack by fast-freezing were significantly slower( P < 0. 05) than these by slow-freezing process,which was in accordance with the sensory results on color,flavor and texture of skipjack. Therefore,fast-freezing in cold brine had advantages on preservation of skipjack onboard.