To improve the expressiveness of speech synthesis, the paper proposes a model to simulate the prosody features of exclamatory speech with modal tags. While compared with reading speech, we found that the major difference between the reading speech and the kind of exclamatory speech is caused by the strong stresses on some modal words and their heavy impacts on adjacent speech units. Then, a CART-based prosody transformation model is introduced to automatically generate the prosody features of exclamatory speech by using reading speech as the baseline. Final perception and comparison experiments have proven the high quality of the model in the simulation of the kind of exclamatory speech.