1. A method for combining panoramic image, which is applied to a camera of a mobile device, comprising: obtaining multiple original images of a same scene, performing folding change and coordinates transformation to the multiple original images, and determining an overlapping area of the multiple original images; establishing a mathematical model of the multiple original images, aligning the overlapping area of the multiple original images, and transforming the multiple original images to a coordinate system of a reference image; and obtaining a space transformation relationship among/between the multiple original images according to the coordinate system of the reference image, selecting an image combining strategy, and completing the combining of the images; wherein aligning the overlapping area of the multiple original images, and transforming the multiple original images to the coordinate system of the reference image comprises: extracting feature points of the multiple original images in a specific way; using a similarity measure Normalized Cross Correlation (NCC) to extract initial feature point pair(s) through a Bidirectional Greatest Correlative Coefficient (BGCC) matching algorithm; getting rid of pseudo feature point pair(s) through a Random Sample Consensus (RANSAC) algorithm to obtain exactly matching feature point pair(s); and performing an inverse mapping transformation to the multiple original images according to a projection transformation matrix, transforming the multiple original images to the coordinate system of the reference image, and performing image registration according to the exactly matching feature point pair(s).