Based on NCEP/NCAR 1°×1° reanalysis data, conventional observational data and the FY 2E satellite data, the physical mechanism of an emergent Yellow River cyclone which induced strong winds over Yellow and Bohai Seas during 26-27 April 2011 is analyzed. It is shown that this event occurred during the period of adjustment of Eurasia mid high latitude circulations, east moving and development of unstable short wave trough at high latitudes and rebuilding of East Asian major trough. A strongly developed Yellow River cyclone was the engenderer of the northerly gale winds. Vorticity advection was a key factor in the growth of the cyclone, and subsequently, temperature advection played an important role. The baroclinicity near cold front was important to the genesis and development of cyclone by transforming available potential energy into kinetic energy. As the cyclone moves, 〖WTHX〗Q〖WTBZ〗 vectors always matched well with divergence maxima, and dynamic and thermal conditions were favorable to accumulate potential energy as well as to enhance and maintain the cyclone. Our results indicate that the strongly development of Yellow River cyclone was associated with vertical coupling between the upper westerly and lower southerly jets, thermal forcing of low level moist warm flow, and subsequently, the ascending motion in lower layers. And the gale winds over Yellow and Bohai Seas resulted from the combined impact of isallobaric gradient, pressure gradient, downward propagation of upper level momentum and divergence of super low level jet.