Active optics technology eases the requirements for the fabrication and stability of mirrors. Optical replication techniques make it possible to fabricate a mirror of optical quality rapidly and inexpensively. Combining the advantages of these two methods, we designed a lightweight unimorph mirror with a diameter of 160 mm based on an Al-SiC passive layer. A finite element model was established to predict the performance of this mirror and to optimize relevant parameters. A spherical prototype mirror was fabricated and tested to measure its shape-correction capability, thermal stability, and surface roughness; this prototype has been used in an innovation project on lightweight active mirrors from the Chinese Academy of Sciences.