Abstract: The article is analysed the formation,dissipation and persistence regularities of the spring sea fog over the middle and northern Huanghai Sea areas according to data obser ved during 1962-1973 years.The authors are of the opinion that two short wave troughes locatad in the middle and lower latitudes transmit eastward, and often add each other under the particular large scale circulation back-ground, thus wa can find that westly trough in the lower latitude develops and moves by north. During the eastward movement of the short wave shoughes the southwest air current in the front of the troughs continuously brings warm and wet air oven the southeastern Xizang Plateau to the northeast diaection and this is an important condition for the formation and development of sea fog. We have constructed relation between activities of the upper cut-off told eddy (in the Caspian Sea-Aral Sea or the northern Indian ocean),the blocked high pressure (in the northern Atlantic Ocean the Ural areas)and activities of the short wave trough,finally also given out mid-range sea fog forecasting method in dtail.