Analysis shows that the severe cold weather in European areas in early 2012 had close relationship with the persistent atmospheric circulation anomalies from low to high level in the troposphere. The strong negative anomaly of the Arctic Oscillation (AO) in Jan. and Feb. was the main reason of this event, making the North Atlantic subtropical high extend eastward and northward together with enhanced intensity. At the same time, it forced the warm and wet air flow along its north side to the Arctic region, which weakened the warm and wet air source in the Europe. Meanwhile, the robust Ural high pressure shifted westward and northward, sustaining the North Atlantic subtropical high, and the polar cold air was enforced to invade southward to the South Europe. The deepened trough in Mediterranean was benefit to the invasion of cold air, leading to the warm and cold air convergence at the north coast of the Mediterranean, whereas the heavy snow disaster occurred in the Appennine Peninsula and the Balkan Peninsula. The AO anomalies had much more effects on the severe cold weather than the La Niña did, though the latter played some roles in the weather.