The invention relates to a liquid culture device for potato virus-free plantlets. The liquid culture device comprises a nutrient pool, a seedbed arranged in the nutrient pool and culture flasks, wherein the nutrient pool comprises a pool body; the pool body comprises a liquid inlet, a liquid discharging outlet and a control valve; a nutrient solution can flow through the liquid inlet and the liquid discharging outlet; the seedbed comprises a bed body and a lifting adjusting device; the bed body comprises a field planting panel and a plurality of field planting holes penetrating through the field planting panel; the culture flasks are arranged in the field planting holes. The invention also relates to a liquid culture rapid propagating method for culturing the potato virus-free plantlets by adopting the liquid culture device for the potato virus-free plantlets. According to the technology, by combining static liquid culture with intermittent liquid culture, the culture of test-tube plantlets has the advantages of higher efficiency and lower cost; besides, the growth cycle of potato test-tube plantlets is shortened, and stem diameter, plant height, leaf area, dry weight and other indexes of the potato test-tube plantlets are all remarkably improved.