In the winter of 2009 to 2010, a rare severe drought struck Yunan Province. This severe drought is due to the lack of rainfall for a long period. The statistical features of the atmospheric circulation and the sea surface temperature for anomalous precipitation in winter over Yunan Province are studied. Furthermore, the severe drought in the winter of 2009 to 2010 is analyzed. Study shows that the occurrence of this severe drought is related to the anomalies of the atmospheric circulation systems in the westerly belt. Positive height anomalies control Lake Baikal and negative height anomalies are sustained over the coastal areas of East Asia, which weakens the northwesterly and force of cold air from the north. Thus cold air can not southward extend into Yunan Province. Espe-daily the Middle East jet stream is weakened. Because a high pressure ridge develops from East Europe to the Caspian Sea. the perturbations of the westerly belt could hardly reach East Asia. Over the Tibetan Plateau there is a high pressure ridge, which leads to the dry northwesterly prevails over Yunan Province. Although the sea surface temperature anomalies in the Pacific can influence the winter precipitation over Yunan Province, it does not give cause for the drought in winter of 2009 to 2010.%2009/2010年冬季我国云南省出现严重干旱,这次大范围严重干旱是较长时期降水稀少所造成的.首先讨论云南省冬季降水偏多和偏少时大气环流和海温的统计特征,基于它们的统计关系,再对2009/2010年冬季我国云南省的严重干旱进行个例对比分析.研究表明西风带环流系统异常是造成这次干旱灾害的主要成因.贝加尔湖为高度负距平,东亚沿海为高度正距平,从贝加尔湖以西到东亚中高纬度西风带较平直,冬季冷空气偏弱,很难影响西南地区.尤其是副热带中东急流减弱,从欧洲东部到里海为高压脊控制,西风带的扰动系统不易东移到东亚上空；青藏高原上空为稳定的高压脊,孟加拉湾南支槽减弱,云南省受异常西北气流控制.对太平洋和印度洋海温的分析表明,虽然海温异常可以影响冬季的云南降水,但海温异常并不是2009、2010年冬季云南省降水偏少的最重要原因.
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