The acquisition of the high-density strain information is of great significance in the aeronautics and astronautics field. Strain can directly reflect the mechanical state of the structure and the structural health state can be inferred from the strain. The optical fiber-based strain measurement technology can densely obtain the distributed strain on the optical fiber, and the strain field distribution on the structure can be obtained by laying the optical fiber on the surface of the measured structure. In recent years, various distributed optical fiber sensing technologies can realize the multiplexing of large-scale sensors on a single optical fiber. Improving the spatial measurement resolution on a single optical fiber has always been a concern in this field. The paper begins by introducing space-intensive strain measurement scenarios and their requirements. It then examines typical distributed fiber-optic strain sensing technologies with millimeter-level spatial resolution, and finally explores the future development direction of dense fiber-optic strain sensing methods.