Abstract: The evaporation duct is an abnormal refractive phenomenon in marine atmosphere boundary layer. It is generally accepted that the evaporation duct prominently affects the performance of the electronic equipment on the sea because of its wide distribution and high occurrence. It becomes the research focus of navy all over the world. Owing to the anomalous distribution of sea and land、coast landform、offshore wind and shoreward wind in shore, it often causes the alongshore effect of the evaporation duct. This effect will debase the veracity of the evaporation duct diagnosis. At present, there are many diagnostic model of the evaporation duct, such as P-J model, MGB model, NPS model and Babin model etc. They are based on Monin-Obukhov similar theory, just it is different that confirms the flux and character scale in the surface layer. These models are only applied for the normality and homosphere in open sea without considering the alongshore effect. Based on this question, this paper introduces the flux-profile relations of Zhang qiang and Hu yinqiao(nonlinear factor ) and the gust item into the Babin model, extends the applicable scope of evaporation duct diagnosis model to the offshore coast and extremely low wind speed. In addition, the author designs an evaporation duct prediction model, coupling the fifth generation mesoscale model (MM5) and the improved Babin model, and uses the observational data and radar data at Ping tan island of Fujian province on May 25-26, 2002 to validate the forecast results. As a result, the outputs of the prediction model are better with the experimental data in 0 to 48 hours, the error of the prediction evaporation duct height is 0.193, and the prediction results are accord with the detection of the radar.