In this paper, the dynamic modeling of a seven linked humanoid robot, is accurately developed, in the three dimensional space using the Newton-Euler formalism. The aim of this study is to provide a clear and a systematic approach so that starting from generalized motion equations of all rigid bodies of the humanoid robot one can establish a reduced dynamical model. The resulting model can be expended either for simulation propositions or implemented for any given control law. In addition, transformations and developments, proposed here, can be exploited for modeling any other three-dimensional humanoid robot with a different morphology and variable number of rigid bodies and degrees of freedom.