The theoretical simulation of the extension structure of high-power GaN-based laser diodes is of great significance to improve the photoelectric performance of GaN-based laser diodes. A green laser diode extension structure with an n-side dual-wave conductor structure was designed. The effect of indium parts in the n-In_xGa_1-xN waveguide layer on its photoelectronic performance in laser extension structure was discussed. And the mechanism of the n-In_xGa_1-xN waveguide layer on the photoelectronic performance of laser diode was clarified. The results showed that when the indium part of the n-side In_xGa_1-xN waveguide layer was 0.07, the photon loss was minimal, and the threshold current was the lowest. When the indium part of the n-side waveguide layer was high or low, photon loss and operating voltage were increased, and meanwhile, the output power of the laser diode was reduced. Therefore, by regulating indium parts in the n-In_xGa_1-xN waveguide layer and controlling the optical field distribution of the outer layer, the photon loss was reduced by 0.2 cm^-1, and the threshold current was reduced by 193.49 mA to 115.98 mA, and the operating voltage was reduced, which increased the output power and electro-optical conversion efficiency of the laser diode, increased the laser output power to 234.95 mW at 6 kA/cm². The n-side dual-waveguide structure design provides theoretical guidance and data support for the preparation of high-power green laser diodes.