1. A method for identifying and positioning a building using a mountain-based outline region restraint, the method comprising the steps of: (1) obtaining a real-time image, detecting a mountain-based outline of said real-time image, and extending said mountain-based outline, wherein obtaining a mountain-based outline restraint region; (2) conducting morphological enhancement and background suppression on said image in said mountain-based outline restraint region; (3) conducting recursive segmentation in said mountain-based outline restraint region, wherein transforming an image obtained in step (2) into a binary image; (4) extracting local regions of interest of a target building in said mountain-based outline restraint region according to said binary image; and (5) directly identifying and positioning said target building in said local regions of interest; wherein step (1) further comprises sub-steps of: (1-1) obtaining said real-time image, and conducting binary segmentation thereon via a maximum variance between clusters method; (1-2) processing said binary-segmented image via a morphological dilation and erosion scheme after conducting medium filtering thereon; (1-3) processing an image obtained in step (1-2) via edge detection thereby obtaining said mountain-based outline; and (1-4) forming a region as said mountain-based outline restraint region by moving said mountain-based outline up and down by Δ pixels, where Δ is 1/20- 1/10 of a height of a current frame of said image.