The Miyako Strait is an important waterway between the East China Sea and the Pacific Ocean. Its hydrologic characteristics at the typical section(KR section)are related to the water exchange between the East China Sea and the Pa-cific Ocean. The temporal and spatial variations of temperature,salinity and density are studied through analyzing the JCOPE2(Japan Coastal Ocean Predictability Experiments 2)dataset. The seasonal and interannual variations of the pycno-cline are examined. The conclusions are summarized as follows.(1)Temperature decreases with depth,from more than 22,℃on the surface to 4,℃ at 1,000,m. The maximum and minimum salinity in vertical profile is located on the subsurface(100-200,m)and at intermediate depths of 500-800,m. Density increases with depth,from less than 22,kg/m3 on the surface to 27,kg/m3 at 1,000,m. The longitudinal-depth variations of isopycnals and isothermalsfollow each other and they both showa depression around the Kuroshio.(2)Beyond 126°E,the development of thermocline undergoes a seasonal cycle of unstrati-fied,growing,strong and decaying periods. Halocline only appears from July to September in the slope and it is thin. The pycnocline has the same temporal and spatial variations as the thermocline.(3)The pycnocline is mainly controlled by tem-perature,except on the surface around 126°E where salinity becomes more important than temperature in determining strati-fication. The total variability(interannual variance and seasonal variance)of squared buoyance frequency is large at the depth less than 100,m and small at the depth more than 100,m. Partitioning of variability between seasonal and interannual scales shows the predominance of interannual variability is at the depth more than 200,m and seasonal variability at the depth less than 200,m.%宫古海峡是连接东海与太平洋的重要水道，其水文要素变化与两者交换密切相关．文中基于海洋再分析数据集JCOPE2(Japan Coastal Ocean Predictability Experiments 2)的温度和盐度模拟结果，分析了宫古海峡典型断面(KR断面)温度、盐度、密度垂向分布的变化特征，讨论了密度跃层的季节分布和年际变化．结果表明：(1)KR 断面温度在表层大于22,℃并随深度降低，1,000,m 左右温度为4,℃；盐度(S)在次表层(100～200,m)达到最大(S＞34.85)，在中层(500～800,m)最小(S＞34.30)；表层密度低于22,kg/m3，随深度逐渐增加，1,000,m左右密度大于27,kg/m3．等密线与等温线分布基本一致，两者在黑潮核心区向下倾斜．(2)KR 断面温跃层在126°E 以东外海区季节变化分为4个阶段，分别为无跃期(1—4月)、成长期(5—6月)、强盛期(7—9月)和消衰期(10—12月)，盐跃层则只存在于7—9月的陆坡处且厚度较薄，密度跃层变化与温跃层一致．(3)密度跃层的分布主要受控于温度，仅在126°E 附近近表层海域受盐度影响．100,m 以浅的海洋密度跃层总时间变化(年际变化与季节变化之和)明显大于中深层，而且黑潮流核处总时间变化明显小于其两侧．水体不同深度的密度跃层主要时间变化机制存在差异，200,m以浅季节变化显著，200,m以深年际变化显著．
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