This paper discusses the long-term temperature variation of the Southern Yellow Sea Cold Water Mass(SYSCWM)and examines those factors that infl uence the SYSCWM,based on hydrographic datasets of the China National Standard Section and the Korea Oceanographic Data Center.Surface air temperature,meridional wind speed,and sea surface temperature data are used to describe the seasonal changes.Mean temperature of the two centers of the SYSCWM had diff erent long-term trends.The temperature of the center in the west of the SYSCWM was rising whereas that of the center in the east was falling.Mean temperature of the western center was related to warm water intrusion of the Yellow Sea Warm Current,the winter meridional wind,and the winter air temperature.Summer process played a primary role in the cooling trend of temperature in the eastern center.A decreasing trend of salinity in the eastern half of the SYSCWM showed that warm water intrusion from the south might weaken,as could the SYSCWM circulation.Weakened circulation provided less horizontal heat input to the eastern half of the SYSCWM.Less lateral heat input may have led to the decreasing trend in temperature of the eastern center of the SYSCWM.Further,warmer sea surface temperatures and less heat input in the deep layers intensifi ed the thermocline of the eastern SYSCWM.A stronger thermocline had less heat fl ux input from upper layers to this half of the SYSCWM.Stronger thermocline and weakened heat input can be seen as two main causes of the cooling temperature trend of the eastern center of the SYSCWM. This paper discusses the long-term temperature variation of the Southern Yellow Sea Cold Water Mass (SYSCWM) and examines those factors that infl uence the SYSCWM, based on hydrographic datasets of the China National Standard Section and the Korea Oceanographic Data Center. Surface air temperature , meridional wind speed, and sea surface temperature data are used to describe the seasonal changes. Man temperature of the two centers of the SYSCWM had diff erent long-term trends. temperature of the center in the west of the west of the SYSCWM was rising ago that of the center in the east was falling. Mandarin temperature of the western center was related to warm water intrusion of the Yellow Sea Warm Current, the winter meridional wind, and the winter air temperature. Summer process played a primary role in the cooling trend of temperature in the eastern center. A decreasing trend of salinity in the eastern half of the SYSCWM showed that warm water intrusion from the south might weaken, as could the SYSCWM cir culation.Weakened circulation provided less less heat input to the eastern half of the SYSCWM.Less lateral heat input may have led to the decreasing trend in temperature of the eastern center of the SYSCWM.Further, warmer sea surface temperatures and less heat input in the deep layers intensifi ed the thermocline of the eastern SYSCWM .A stronger thermocline had less heat fl ux input from upper layers to this half of the SYSCWM.Stronger thermocline and weakened heat input can be seen as two main causes of the cooling temperature trend of the eastern center of the SYSCWM.