In the High-power InGaN/GaN-based LED structures, p-AlGaN layer plays a role as electron blocking layer. In this paper, GaN/InGaN-based LED have been grown on sapphire by metal organic chemical vapor deposition (MOCVD), and the p-type doping mechanism and structural optimization of AlGaN layer were studied. The ways to change AlGaN components have been discussed. We found that the growth temperature, growth pressure and flow TMAl (mole ratio) have strong effect on the Al components through different mechanisms. In the AlGaN electron blocking layer, the Al composition is between 10%—30% and the electron could be well limited to the quantum well region, maintaining a high quality crystal material. The p-type doping efficiency of AlGaN layer is low, and there is a magnesium droop problem due to lack of hole injection. A new growth method is suggestece to solve the problem. Grown under optimal conditions, the p-type AlGaN inserted in a LED structure greatly improves the output optical power of LED device.