Abstract: As important urban facilities,underground pipelines perform the functions of energy transfer and information transmission,providing convenience and guarantee for urban life.Ground-penetrating radar (GPR),as a high-resolution,high-precision,trenchless,and non-destructive detection technique,has great advantages in pipeline surveys.However,undulating surfaces with complex terrain greatly influence GPR-based detection of underground pipelines.Therefore,this study conducted numerical simulations of the underground pipeline detection using the finite element method,which can be combined with an unstructured grid to fit the undulating surfaces effectively.Furthermore,this study introduced the height correction method to match the obtained geologic sections with terrain,making it easier to analyze the anomaly characteristics.Finally,through numerical experiments,this study analyzed the influence of undulating surfaces on the detection of pipelines with different burial depths,spacings,materials,and fillers,providing a theoretical basis for GPR data interpretation.The experimental results show that waveforms and reflected wave energy,subjected to distortion due to surface undulations,cannot be used as the sloebasis for judging pipeline information.Therefore,height correction is required,and the vertexes of hyperbolas can be used to judge the burial depths and materials of pipelines.