There was occurred a strong wind process from 31 December 2014 to 1 January 2015 over the Bohai Sea, which has the characteristics of strong burst, long duration, strong winds with three wave peak of wind Speed. The reanalysis data of NCEP/NCAR are used in the diagnosis and analysis of the offshore wind induced by strong cold air. The analysis shows that when the cold air affected the Bohai Sea, the warm and cold air contrast enlarged the lowlevel front zone, and wind force increased obviously. Three fluctuations of the Bohai Sea wind correspond to the low layer cold advection strengthening, and temperature advection and vertical structural variation indicate that above the deep cold advection from top to bottom formed a retroverted cold advection transport channel, which transmitted the cold air to the lower levels for three times, corresponding to the three peaks of wind fluctuation. The highlevel downward momentum transformation played an important role in the rapid growth and maintenance of the strong winds. The three wind speed fluctuations over the Bohai Sea are related to the highlevel downward momentum transformation and the higher the radial degree of the air flows, the stronger the momentum transformation at the upper levels, the greater the wind speeds on the ground were.