Abstract: Aimed at the inaccuracy and low reuse rate of functional component extraction in embedded systems reconstruction, a procedure suitable for embedded system functional component extraction is presented in this paper. A component model is established conforming to the characteristics of embedded systems, and a formal description of the model is given. According to the component model, firmware code functional component is implemented and extracted layer by layer using cluster analysis method based on coupling measurement. Functional component verification method is proposed based on model verification. By contrast experiment, this method greatly improves the accuracy of functional component extraction in embedded systems reconstruction, and enhances the reusability of original system.