To realize ultra-lightweight ratio, mirrors were fabricated with CFRP (carbon fiber reinforced plastic composites) by replication technology. The replication technology was aimed to improve surface accuracy. Though replication technique, the surface accuracy was improved to 0.098 λ (λ=632.8nm, RMS), and the roughness of 1.9 nm (Ra) can be achieved. The CFRP mirror presented poor dimension stability, the surface accuracy increased gradually in air. In order to solve this problem, a polymer coating was carried on mirror surface. The polymer coating exhibited better dimension stability, the surface accuracy can be maintained under 0.15 λ for more than 200 days. © 2019 SPIE.