Cultural relic reproduction is an important foundation for the conservation, inheritance and development of cultural heritages (especially super-large immovable cultural relics). The development of emerging technologies such as 3D laser scanning and 3D printing provides new ideas for cultural relic reproduction. Taking Cave 18 of Yungang Grottoes as the research object, this study explored and established a high-fidelity copying technology system for super-large cultural relics, which mainly includes high-fidelity data acquisition, 3D reconstruction, model block, printing and installation as well as high-fidelity paint printing. This method has been applied to the high-fidelity equal-proportion reproduction project of large-scale grottoes such as Cave 18 of Yungang Grottoes. The results show that the method proposed in this study can realize the high-fidelity equal-scale reproduction of large-scale grottoes, and the reproduction performances met the requirements of movement. This method could provide some reference and guidance for the conservation of similar cultural heritage objects.