Abstract: Aluminum finned ferromagnetic tubes are widely used in heat exchangers. It's in-service inspection is difficult in NDT technology. This paper shows research on near field eddy current testing technique in Aluminum finned ferromagnetic tubes inspection. The result shows that this technique has the ability to detect through hole and axial cracks, inner or outer wall circumferential cracks and large area wall thinning. The defect on edge or below the support plate can also be detected in some extent.