The paper presents a tool to transform Simulink models into UML models. The embedded control software design process can be divided into the control logic design phase and the software design phase. MATLAB/Simulink is widely used to build a controller model in the control logic design phase. On the other hand, UML is widely used in the software design phase. We have developed a model transformation tool to automatically transform Simulink models with state transitions, conditional selection of data ows or conditional selection of control ows. The model transformation tool analyzes the data ows and control ows of Simulink models and generates UML models with ef cient control ows. We have applied the model transformation tool to a number of Simulink models and have con rmed its usefulness for embedded control software design.