This paper describes the design and implementation of a reconfigurable modular humanoid robot architecture. Our proposed architecture features three key concepts, 1) a reconfigurable mechanical structure, 2) a layered software model, and 3) an end-to-end real-time communication mechanism. Our proposed reconfigurable modular humanoid robot consists of several functional robots such as an arm robot, a mobile robot, and a head robot to realize an effective reconfigurable mechanism for expandability. Depending on many purposes of researchers and users, our reconfigurable modular humanoid robot can be used as some kinds of humanoid robots or as several autonomous functional robots. We design and develop a prototype modular humanoid robot consisting of five functional robots for evaluating our proposed architecture. The results of the experiences show the modular humanoid robot can achieve expandability by our reconfigurable mechanism.