Based on the calculation and analysis of the velocity spectra of the theoretical geological model for six horizontal homogeneous bedded media under the condition of typical topographic relief, this paper points out that the utilization of the conventional horizortal base level technique for extracting stacking velocity under the complex topographic condition fails to attain the precision of velocity and will produce false longitudinal and latitudinal velocity variation regularity. It is also demonstrated that the use of the slipping base level method to extract stacking velocity can not only eliminate the effect of topographic relief but also satisfy the velocity precision of seismic exploration. In addition, the method can reflect the real interval velocity.