Abstract: The frequency band below 300 kHz is an important spectrum resource for radio systems such as deep-sea, deep-earth, deep-space exploration, long-distance communication, navigation etc. Their radio wave propagation characteristics continue to attract attention and development. This paper mainly introduced the research progress of China Research Institute of Radiowave Propagation and relevant domestic cooperative teams in this field. In view of additional secondary phase factor (ASF), which has important influence on the ground-based navigation timing system, a modified ASF model which combines theory with experimental measurement and meets engineering requirements is developed. In order to solve the problem of underwater target detection and electromagnetic radiation, a finite-difference time-domain (FDTD) calculation method for radio wave propagation across the sea surface (bed) is developed. Compared with the traditional integral equation, this method has greatly improved the ability of solving complex problems. Aiming at the satellite-Earth link problem involved in space environment detection and application, based on the three methods of total method, integral equation and FDTD, the problem of transdielectric propagation calculation of ground-based or space-based very low frequency (VLF) radiation source is solved, and the theoretical method of analyzing the anisotropic ionospheric midline antenna is established. In order to solve the long-distance propagation problem of VLF ground-ionospheric waveguide, finite element method (FEM) and calculation fusion method are developed on the basis of traditional waveguide mode theory. The former provides a solution for the wave mode conversion in the diurnal transition zone, and the latter lays a foundation for the high-precision prediction of propagation link. Finally, from the calculation method and the physical parameters used in the calculation process, the research prospect is put forward.