A gale with wind force scale 8 occurred in the Bohai Sea and Shandong Province on 15 April 2009. The gale is severe strong, but lasts only a half day. Wind speed strengthens significantly near the Bohai Sea and Shandong Province. With the conventional surface data and NCEP analysis data, the causes for this gale event are diagnosed. Results show that the gale is affected by the cold front near the surface and the vortex at the upper level. The cold advection spreads downwards from the upper level during the southward moving of the cold air, as a result, the cold advection and the cold air under the 850 hPa both strengthen. When the cold air arrives at the Bohai Sea, the strong cold advection behind and the strong warm advection in front of the cold air at the low level make the frontal zone further strengthening. The downdraft of the secondary circulation is corresponding to the positive allobaric area near the surface. The strong allobaric wind and the large scale baric gradient wind both lead to the abnormal gale together, and the corresponding severe gust wind is probably related to the impulse of the secondary circulation.