The mechanical analysis of adhesive repair of honeycomb sandwich composite plate is more complicated than that of the laminated plate repair, because not only the laminated damage, but also the honeycomb buckling should be considered. Experimental and numerical investigations are carried out to understand the damage propagation and ultimate strength of both open-hole and repair plates under compressive load. The results of numerical models are verified by experimental data and they are found in good agreement. It is revealed from the results that the strength of open-hole plate is about 34% of the strength of intact plate, while the strength of repair plate could resume to 76% of that of intact plate after the repair process. It is found that the structure strength increases as the scarf repair angle decreases due to the decline of shear stress in the adhesive. We also present the optimum ply sequence and the optimum number of overlays in considering the improvement of structure strength. This research will be useful in improving the design and analysis techniques for scarf patch repair of sandwich structures.