Based on station data and NCEPFNL 1°×1° reanalysis data from 2008 to 2012, the developing Yellow River cyclones passing over Bohai Sea are classified into Summertype and Springtype. In this paper, the structures and impact factors of the two types of cyclones, especially the moisture, thermal and dynamic effects of the HuangBohai Sea are compared and analyzed. It is shown that the Summertype cyclones are related to the wide area of heavy rainfall, while the Springtype cyclones are related to large gale area instead of rain. The structures of the cyclones are baroclinic, but Summertype cyclone is with a warm center, while Springtype cyclone has remarkable baroclinicity. Upperlevel jet is at the south of cyclone in spring, the cyclonic wind shear at the jet left side keeps the cyclone, and the upper level momentum passes down into the back of Springtype cyclone, and meets the cold front secondary circulation and the flat sea surface, which is conducive to rapidly increasing lowlevel cyclonic winds. In comparison, the upper level jet is at the north of cyclone in summer, and the upperlevel divergence of the jet right side and lowlevel convergence strengthen together the ascending motion of summer cyclone, favoring strong cyclonic precipitation and condensation latent heat release. There is conversion of perturbation potential energy to kinetic energy when cyclones develop through the Bohai Sea that maintains and strengthens the cyclone momentum. In addition MPV calculations show that Summertype cyclones are with the deep and thick dry air sinking, which is favorable for the formation of heavy precipitation, but in Springtype the drywet gradient is small and distributes in scattered patterns, corresponding to the smallscale precipitation. HuangBohai Sea is the main vapor transport channel of cyclones which transports abundant moisture in summer because of the higher sea surface temperature than in spring, but the water vapor transport is deficiency in spring. The low level wind speed of Springtype cyclone is significantly enhanced by sea surface dynamic effect, while the effect does not work in Summertype cyclone. Diabatic heating analysis over Bohai Sea indicates that latent heat plays an important role in Summertype cyclone, while the sensible heat is more significant in Springtype cyclone.