1. A method of obtaining a panoramic image, comprising steps of a) obtaining panoramic images of regions of interest to be taken in an object, wherein the panoramic images are correspond to multiple image-layer-traces: b) dividing the multiple image-layer-traces into a plurality of regions respectively and determining at least two analysis regions; c) selecting an optimal image-layer-trace closely related to a focus-trace by analyzing the multiple image-layer-traces in the same analysis region: d) extracting a connecting-trace linking the optimal image-layer-traces selected in the regions; e) completing a final-trace by connecting the optimal image-layer-trace selected in each region and the connecting-trace all together; and f) reconstructing a panoramic image corresponding to the final-trace.