Digital twin has been listed in the top ten strategic technology trends for four consecutive years. Its deep integration with the library has certain value and significance for exploring the new operation mode of the library in the 6G era. In this paper, starting with 6G technology research and development in China, the development process of digital twin technology is briefly discussed, the possibility of digital twin and library technology integration in 6G era is analyzed, the concept of twin library is put forward, its connotation characteristics, theoretical logic and practical requirements are discussed, and its operation mechanism and theoretical framework are designed. The research holds that the deep integration of library and digital twin is inevitable in 6G era, and the twin library may become a new model of library development in the future.