Abstract: Focusing on the typical loess surface structure in the Xiaoyi area, Shanxi Province, China, this study elaborates on the geometry selection, data processing, and data interpretation of the microlog survey method with sources in the borehole and receivers at the surface, and achieve several findings. The microlog survey via in-borehole seismic wave excitation exhibits encouraging source-media coupling effects, clear first-break onset, and seismic records with high signal-to-noise ratios (SNRs). Given the presence of source-receiver offset in microlog survey data, the inclined ray path from the shot point to that the receiver point should be corrected to a vertical path. Based on the correction equation, the source-receiver offset should be less than 10 m in practical applications. The loess structure in the study area shows significant vertical stratification. At the cliff, the seismic velocity on the side near the collapse section is significantly lower than that on the side far away from the section, with vertical fractures distributed within the loess layers. Literally, the P-wave velocity varies with the observation azimuth due to heterogeneous local compaction, presenting a quasi-elliptical distribution pattern overall. Therefore, the circular-array geometry can enable the microlog survey to investigate the velocities and thicknesses of low-velocity zones in loess and to characterize the velocity heterogeneity across various loess layers.