Abstract: Pre-stack depth migration is widely used in seismic data processing, and the result of such pre-stack migration is an important factor in seismic geometry evaluations.Generally, quantitative evaluations of the seismic geometry based on the resolution of migration imaging can guarantee optimal imaging results when designing seismic acquisition.At present, the seismic geometry evaluation method based on migration imaging resolution is primarily based on double-focus analysis, which requires wave field continuation in the realization, resulting in a low calculation efficiency.In this study, an improved Gaussian beam method is used to enhance the calculation efficiency of the conventional double-focus analysis.This method includes the following steps: a.using Gaussian beam propagation based on Snell's law with a limited frequency and a viscoelastic medium model to generate a CFP gather of a target point; b.implementing double-focus calculation in the plane centered on the target point according to the ray tracing result; and c.using the width of the main energy as the migration imaging resolution to evaluate the geometry.In this method, the effect of Fresnel zones is considered during ray tracing, and the effect of the Q factor is included in dynamic tracing, with a consideration of the frequency changing of wavelets; these improvements enhance the reliability of the calculation results.The principle of this method is consistent with pre-stack depth migration.Model application results indicate that this method can efficiently and reliably realize quantitative evaluations of the seismic geometry based on migration imaging resolution for a certain target point or target layer underground.Hence, this method presents high feasibility for the design of 3D seismic surveys of complex geological targets.