This work studied the possibility of the application for Metal Matrix Composites (MMCs) in extendible exit cone nozzles (EECNs), through analyzing the stress distribution on the solid rocket motor’s EECNs. The result shows that the MMCs can be used on the EECNs. With replacing the traditional steel by light MMCs to serve as the key supporting components, the strength and stiffness can satisfying the application request. The mass of the components are drastically decreased. This technique has promising applications.