A rather complete sea ice model is given, which deals with not only thermodynamic and dynamic processes commonly used in previous models of sea ice but also a melting process of ice driven into warmer waters.A series of numerical experiments have been carried out in order to search after a mechanism of the growth and decay of sea ice in the Bohai sea, and the principal result shows that the melting process of sea ice driven into the warmer waters must be taken into consideration when the ice condition in such a partially frozen sea as the Bohai Sea is calculated.