通过对Ｌｅｖｉｔｕｓ气候平均的海洋温度盐度资料分析，在认识南海混合层季节演变特征的基础上，探讨了南海温跃层的结构，揭示了南海北部冬季温跃层通风现象．分析表明，冬季南海北部温跃层的主要通风层次为２２．０－２３．５的等密面，其下是未通风湿跃层．冬季南海温跃层的通风过程伴随着北部混合层的水团在抬头线处下沉并向南运动．在水平结构上，上述信号沿着等位势涡度线运动，维持位势涡度守恒． Based on the analysis of the Levitus climatological mean salinity data of the ocean, based on the understanding of the seasonal evolvement of the mixed layer in the South China Sea, the structure of the thermocline in the South China Sea is discussed and the winter thermocline ventilation in the northern South China Sea is revealed. The analysis shows that the main ventilation layer of the thermocline in the northern South China Sea in winter is the isoptic surface of 22.0-23.5, and the unventilated wet layer under it. The winter warmth in the South China Sea is accompanied by the aeration process where the water mass in the northern mixed layer sinks and moves southwards at the head-up line. In the horizontal structure, the above signals move along the equipotential vorticity line, maintaining the potential vorticity conservation.