The twin-core fiber is a crucial passive optical devices, it has played an irreplaceable role in the areas of the optical communication and optical sensing. Firstly, the structure, classification and the latest manufacturing technique of present fibers are introduced. And according to the special structure characteristic of twin-core fibers and the spectrum characteristic causing by the coupling characteristic between two cores, the application of twin-core fiber in the area of fiber sensing and optical communication are described. Lastly, the hot words corresponding to two-core fiber over the past decade are showed by the data knowledge platform. And the development trends and prospects of the twin-core fiber in future 10 years are analyzed.