Pulse compression grating plays very important role in the laser confinement fusion system. Along with the development of laser confinement fusion project, more and more large aperature gratings are needed. Holographic technology is very important means to manufacture large aperature gratings, but the aperature of gratings is limited by the recording system. In order to create large aperature pulse compression grating, the method by several times exposure to fabricate large aperature mosaic gratings is investigated in this paper. The method use a reference grating as a detecting devices to test the phase matching situation between the recording light wave and the recorded grating. By using stripes locking system to control the phase of light wave, the goal of manfacture large aperature compression mosaic grating will be achieved. At last, the mosaic grating experiment is studied. The grating frequency is 1740 lp/mm and the alignment accuracy is better than 30 nm.