Abstract: In order to verify the effectiveness of the non-contact magnetic detection of the small-caliber natural gas long-distance pipeline in the mountain area, magnetic induction intensity gradients ∂B_x,∂B_y,∂B_z in the three directions above the pipeline were obtained. The stress risk level was determined, and the results of non-contact magnetic testing were verified by excavation using metal magnetic memory testing technology and ultrasonic thickness measurement technology. Engineering application result shows that under non-excavation conditions, non-contact magnetic detection technology can effectively identify the stress concentration location of mountain small-diameter pipeline and analyze its damage level, improving pipeline inspection efficiency. Therefore, it is a scientific and effective detection method.