There’s an existing problem on linear structure that, the farther the array probe is located on coil’ s inner diameter, the smaller is the peak of differential signal of the same position defect. Aiming at solving this problem, this paper put forward an approach of placing the TMR sensor in the shape of semicircle with same horizontal spacing within the same excitation coil, and designed a new type of pulse vortex C-scanning imaging device. The findings suggest that, contour maps drawn after C-scanning and the conversion and threshold segmentation of scanning results could well reshape different forms of cavities on copper plate and successfully gained the 2D images of them, thus proving the effectiveness and feasibility of this approach.