Abstract: The deployment and locking of solar arrays of a free-floating spacecraft is studied in this paper. The rigid-flexible coupling dynamic model for describing the deployment and locking process is established using the Jourdain's velocity variational principle and the approach of forward recursive formulation. The contribution of joint friction to the dynamic equation of the system is derived based on the virtual power principle. The 3-D bristle friction model is introduced to study the influence of joint friction on the deployment dynamics of solar arrays. The validity of the proposed model is verified through the comparison of simulation results with those using the commercial software ADAMS and NASTRAN, and this model is available for predicting the deployment process of solar arrays and the attitude motion of spacecraft.