The South China Sea(SCS)is one of the largest marginal seas in the Western Pacific and sensitive to climate changes. Emilimia Huxley and Gephyrocapsa Oceanica can produce a compound with 37~39 carbon atoms which we call long chain alkenones in the process of growth and metabolism. The unsaturation of this alkenones is $U_{37}^K$. The sea surface temperature (SST) variation process of the Beibu Gulf during the last 10 thousand years has been reconstructed based on the sediment core SO-31 (location 18°36'46.45"N,107°22'43.20''E,core length 7.34 m)by using the organic thermometer $U_{37}^K$. Overall,the SST of the Beibu Gulf has been increasing gradually for the last 10 thousand years. The highest temperature is 28.0 ℃ at 255 a BP and the lowest is about 22.0℃ at 2658 a BP with an average of 25.4℃. The SST has an overall increasing trend during the Holocene,but increasing obviously during the last 1.3 ka. The fluctuation amplitude is low between 10.0 ka BP and 5.3 ka BP,but becoming large since 5.3 ka BP. For the last 5300 years,SST has a one hundred scale periodic time,which might be related to the double century cycle of total solar irradiance. In addition,the core has recorded 8 temperature events with regional significance including 6 cold events at 9.2 ka BP,5.3 ka BP,4.3 ka BP,2.7 ka BP,1.3 ka BP,0.6~0.2 ka BP and 2 warm events at 6.9 ka BP, 0.9 ka BP. The Beibu Gulf SST fluctuation during the last 10 ka is mainly controlled total solar irradiance,East Asia Winter Monsoon and even high latitudinal ice melting events. Meanwhile,volcanic eruptions and reducing cosmic rays are also important to SST changes during the last 1 ka.