The cantilevered support for space mirrors is a design challenge in remote sensing devices. Traditional structures made of materials such as cast titanium and carbon-silicon carbide cannot simultaneously meet the requirements of high lightweight, high support stiffness, and unconventional configurations. In this study, a high lightweight 3D-printed titanium alloy structure with a lattice in the skin was adopted to support the suspended mirror in a remote sensing camera. First, topology optimization was used to obtain a concept design for the support structure. Based on this conceptual design model, the geometric model was reconstructed using Creo software for shell extraction. The lattice structure was then filled using specialized software, and a lattice-in-skin 3D-printed model was established. Finally the HyperWorks software is used for finite element analysis of the skin and lattice. Iterative optimization was performed on skin thickness, lattice size, and local reinforcements. The support structure was fabricated through 3D-printed additive manufacturing and validated for its effectiveness through the dynamic test and CMM (coordinate measuring machine) measurement. This proposed method effectively addresses the support issue of suspended, unconventional mirrors and provides a valuable reference for the design and application of 3D-printed titanium alloy structure in remote sensing devices.