1. An above-ground building recognition method, comprising the following steps: (1) taking an infrared image of the ground from the air; (2) performing detection and positioning in the infrared image to determine a suspected target; (3) aiming at the suspected target to perform laser imaging; (4) performing range gating on a laser image to filter out foreground and background interference; and (5) extracting a shape feature of the suspected target from the laser image with interference filtered out, taking the shape feature as a target matching element to perform matching with a target shape feature template, and fusing a matching result and a local contrast feature of the suspected target in infrared imaging, so as to recognize the target, wherein a specific implementation manner of step (5) is that: calculating a ratio of a local contrast value of the suspected target in infrared imaging to a local contrast threshold, wherein the ratio is marked as a local contrast a of the suspected target; calculating a similarity b between the target matching element and the target shape feature template; and calculating a target recognition probability p=k1*a+k2*b and a weight coefficient k1+k2=1, wherein k1≦k2, wherein a target having the maximum target recognition probability is a target recognition result.