With the acceleration of urbanization, the number of various underground chambers in cities is continuously increasing, posing new challenges for geological radar detection. Aiming at the problem of unclear imaging characteristics of geological radar detection of elliptical cavities, the entire process of geological radar scanning was taken as the research object through theoretical analysis. The images of radar ground-penetrating scans of underground elliptical cavities were divided into three stages, and the corresponding relationships between echo signals and horizontal positions at different stages were established. The changes in geological radar scan images of elliptical cavities under different burial depths and different geometric parameters were systematically analyzed. Combined with practical engineering detection cases, a scientific explanation of the imaging mechanism of geological radar for elliptical cavities was provided. The research results show that the imaging mechanism of elliptical cavities in ground-penetrating radar is generally consistent with actual working conditions, confirming that the imaging mechanism of elliptical cavities can accurately analyze the location and development level of underground elliptical cavities, and can provide theoretical support and reference for subway tunnel construction and the subseque-nt investigation, prevention, and control of urban road hazards.