In order to meet the requirements of automatic assembly of equipment in the spacecraft cabin and obtain an assembly robot with small structure size, large workspace, high load capacity and high flexibility, a lightweight, high-load 8-DOF hybrid attitude adjustment robot cabin assembly system based on PRR/PR(PRR) R mechanism was proposed. By analyzing the position mapping relationship, velocity mapping relationship, Jacobian matrix and acceleration mapping relationship of the hybrid assembly robot, the dynamic model of the hybrid assembly robot was established, and the mapping relationship between the driving force, driving torque and joint speed was obtained. Furthermore, the stiffness model of the hybrid robot was established to solve the deformation degree of the mechanism after six dimensional force was applied to the end of the mechanism. ADAMS and ANSYS simulation models verify the kinematic, dynamic and theoretical stiffness models of the mechanism. It provides a feasible scheme and theoretical basis for the realization of large equipment assembly automation in a narrow and long space.