The forecasting effect of convective parameters output by MM5 model is tested with the data of 20 thunderstorm cases. The results show that the model output convective parameters can reflect the difference between the storm and no storm days and can forecast the happening time and area of the storm. The storm can be judged not only through parameter values but also through the changing tendency of convective parameters. At the same time, the model output still need to be improved because the difference is obvious compared to observation data and the different time range outputs is so varied.