High-efficient GaN-based laser diodes (LDs) with tunnel junction are designed by replacing conventional p-type AlGaN cladding layers and p-type GaN contact with lower-resistant n-type AlGaN cladding layers and n-type GaN contact. In addition, the characteristics of the LDs with tunnel junction are numerically investigated by using the commercial software lastip. It is found that the performance of these LDs is greatly improved. As a comparison, the absorption loss and non-radiative recombination are greatly reduced. The threshold current and series resistance are decreased by 12% and 59%, respectively, and the slope efficiency is raised up by 22.3%. At an injection current of 120 mA, the output power and wall-plug-efficiency are increased by 34% and 79%, respectively.