Abstract: Based on the triangle-truncation for wavenumber 10,a study is made of the topographic influence on the low-frequency oscillation in terms of a 5-level low-order global spectral model.The analysis of the one-year band-pass filtered data obtained by models with and without topography shows that the low-frequency waves forced by topographic have seasonal characteristics. The low-frequency waves are produced directly by the forcing of topography in northern winter. But the low-frequency waves come from the tropic heating source which is related to the forcing of topography in northern summer.The results also show that the variability of equatorial zonal wind is caused by the low-frequency waves which are forced by topography in the northern hemisphere and that the varibility of equatorical zonal wind produces new low-frequency waves in the southern hemisphere. In this case,the low-frequency waves can propagate through the equator for interaction between the northern and southern hemispheres.