Abstract: Investigating the surface geological structure is a crucial link of seismic acquisition, playing a significant supporting role in guiding the formulation of construction countermeasures and providing key parameters for data processing. In view of the complex soil layer structure and intense igneous rock undulations in the surface geological characteristics of the QL3D area of Gaoyou Sag, a seismic surface investigation method combining shallow refracted waves and surface waves was proposed. The method leveraged the propagation characteristics and medium sensitivity of both wave types, used the shear wave velocity of the marker layer as a medium, and constrained the inversion and interpretation of surface wave data with refracted wave observations. This method effectively increased the sensitivity and resolution of the surface investigation results. Field experiments conducted in the QL3D demonstrate that compared to traditional shallow refraction methods, the refracted wave and surface wave joint analysis method improves the effective detection depth and area of top interfaces of igneous rocks without greatly increasing construction costs. Meanwhile, it enhances the ability to depict the surface soil structure and the undulating trend of igneous rocks in this area, clarifies the main factors affecting the quality of seismic data acquisition in this area, and thus provides suggestions for the deployment of observation systems for different blocks within the area.