A semiconductor laser linear array of the iffraction grating array exocoele and its preparation method is provided, which belongs to the field of semiconductor laser and comprises a semiconductor laser linear array, a fastaxis collimation lens, a slow lens, a half wave plate, a high-aperture lens and an iffraction grating array. The said semiconductor laser linear array is characterized in making exocoele feedback through the iffraction grating array to make one or more luminescent units of the semiconductor laser linear array incident onto the corresponding iffraction grating unit. By adjusting each of the iffraction grating units, the central wavelength of the luminescent unit in different degrees of crook through the iffraction grating unit and the feedback light retraced back are equal or closely similar with each other, thus the whole spectral line width is reduced. The invention has the advantages of using a plurality of small-area gratings, low cost, easy processing, simple light path adjustment and high output power.