The effect of water temperature on the ventilation in the Pacific oyster Crassostrea gigas was examined by the direct measurement method of ventilation volume. The water temperature was elevated 3℃ every hour. The ventilation volume increased from 1.32 l/min/kg at 20℃ to 2.35 l/min/kg at 26℃ with the rise in the water temperature, and then decreased to 0 l/min/kg at 37℃. The moving speed of vinyl film put on the gill surface (activity of ciliary movement) increased from 31.3 mm/min at 20℃ to 56.3 mm/min at 35℃ , and then decreased to 0 mm/min at 41℃. These results reveal that the Pacific oyster would increase the preying quantity by the increase of the ventilation volume with the rise in the water temperature.