Coherent beam combination is an effective method to get a high power beam. Two-dimensional (2D) sine phase grating of special design is a perfectly combining element. The design of 2D sine phase grating is introduced, and computational results indicate that the high splittering efficiencies are 81.1% and 73.1%, which increase 37% and 26.9% compared with conventional Dammann gratings respectively in the case of 3×3 and 4×4 beam-splitting. The fabrication of 2D sine phase grating and errors are analyzed , and the results show that coupling efficiency of combination has a maximal value leading to greater error latitude for the fabrication of sine phase grating. Splittering and combination light field are different on phase grating surface. The coupling efficiency can be improved, if the phase grating is only used for combination.