The laterally coupled DFB-LD shows unique advantages to achieve single longitudinal mode LD, which has attracted the attention of researchers both at home and abroad in recent years. The laterally coupled DFB-LD can not only effectively solve wavelength stability problem of a LD, but also can realize high performance devices owing to its easy preparation technology. It is of great importance to the development of small, efficient and low-cost wavelength locked semiconductor lasers. In this paper, we analyzed laterally coupled DFB-LD in terms of its structural characteristics, operating mechanism, and output characteristics. As the grating position is different from that of the traditional Bragg grating, different fabrication means are explored and compared. Therefore, its progress over the world is reviewed, and its wide applications are forecasted.