Based on Parkinson and Washington(1979)thermodynamic sea ice model,China Bohai Sea geography and climatology,introducing a slab ocean assumption and the bisection method for calculating the ice surface temperature,using the monthly data including total cloud cover,relative humidity,sea level pressure and wind speed,together with monthly averaged surface air temperature at 4 surrounding coastal weather stations as the forcing field,the Bohai Sea ice climatic variation are simulated.Simulated results and observed annual sea ice grades have a similar variation trend,thus proving that air temperature is a decisive factor for the inter-annual variation of Bohai Sea ice.