Abstract: Studying the impact of the ionosphere on low-frequency sky-wave signals is of great significance for its application in long-distance navigation and timing. In this paper, combining the international reference ionosphere (IRI) electron density model and the NRLMSISE-00 atmospheric model, using the quasi-one-dimensional bilinear transform finite-difference time-domain method of plane wave propagation in a layered half space, the reflected signal of low-frequency sky wave reflected by the ionosphere is calculated, and the variation of the amplitude, time delay and multipath of the reflected signal with the angle of incidence, time of day, and season are analyzed. The simulation results show that: as the incident angle increases, the amplitude of the reflection coefficient first decreases and then increases for TE wave; the amplitude of the Loran C low-frequency sky wave signal reflected by the ionosphere in a day differs by up to 32.22 dB, and the time delay difference can reach 69.03 \textμs; the Loran C sky wave signal reflected by the ionosphere generally contains a complete Loran C signal, and contain two signals during the transition between day and night.