This paper develops a novel multi-mode deployable metamorphic aerospace mechanism for aerospace equipment, which is composed of a double-mode base mechanism, six metamorphic kinematic chains, and the self-locking and unlocking mechanisms. The scissor-shaped mechanism is used to afford a good deploy/fold ratio for convenient storage and transportation, the multi-loop truss-shaped structure is adopted to obtain a good stiffness property, modular and lightweight designs are applied to enhance the expandability for different aerospace tasks. Besides, a mobility bifurcation method is used to realize the transformation between the deployment motion and the bending motion. Based on the special structural design and connection method, the aerospace mechanism can be assembled and multiple motion modes can be realized, which can be used for five types of space attack-defense equipment including the space robotic grasper, the reconfigurable robot, the crawling robot, the supporting mechanism for solar array, and the supporting mechanism for large deployable antenna. The specific design and assembly methods of the aerospace mechanisms are introduced in detail, and motion analysis is then conducted. Finally, five types of key potential applications are simulated to verify their effectiveness and feasibility.