Abstract: In this paper, the propagation characteristics for rays and wave normals of VLFradio waves through the low-latitude ionosphere based on the 3-Dray tracing computation carried out for whistler mode waves are investigated by using an IGRF (1980) model. It is found that the ray paths of whistlers detectable on the ground can stably remain in a region around geom. lat. 10° for various ionospheric profiles, and that the downcoming rays focus remarkably in the same region, with a focus gain about 10.4 dB Besides, the results of computation show that the lowest latitudes of non-ducted whistler paths exhibit sharp cut-off near geom. lat. 6.5°.