In this study the temperature at different layers (5 m, 50 m, 100 m and 200 m) and the temperature structure (difference of water temperature between 100m and 200m) in the fishing ground of O.bartramii are analyzed based on the fishing data from Chinese squid jigging fleets in the northwestern Pacific Ocean and temperature data from August to October in 2003-2007. The results indicate that the fishing ground of O.bartramii is distributed in the waters of 151-156°E and 41-44°N during August and October, and the monthly temperature vertical structure is different in the fishing ground of O.bartramii. The optimal range of temperature at 5 m, 50 m, 100 m and 200 m layers and the difference of temperature from 100m to 200 m in the fishing ground of O.bartramii are 17-21 ℃, 9-12 ℃, 3-9 ℃, 2-7 ℃ and 0-0.03 ℃/m respectively in August. And they are 15-18 ℃, 8-11 ℃, 3-6 ℃, 2-5 ℃ and 0-0.02 ℃/m respetively in September, 14-17 ℃, 7-9 ℃, 2-8 ℃, 3-6 ℃ and 0-0.02 ℃/m respectively in October. The results also indicate that the fishing ground is distributed in the warm side of front at different water layers.