The detection and recognition of specific targets is one of key techniques of ATR. The recognition of a runway, as a specific ground target, is still an interesting research subject in the ATR. An algorithm of automatic runway recognition based on multi-scale linear object enhancement is presented according to runway characters of linear structure and high intensity. Experimental results show that the algorithm can enhance runway while restraining other objects of nonlinear structure and has better performance than the algorithm based on edge detection in the complicated background.