The 1×1 multi-mode interference (MMI) coupler structure has a large multi-mode waveguide, which can increase the gain area of active photoelectronic devices such as laser diodes and superlight-emitting diodes and realize the improvement of output power. Most of the traditional 1×1 MMI regions are designed as rectangles, and the large symmetric optical mode interference density increases the sensitivity of the output light intensity to the MMI structural parameters. To solve this problem, we design a 1×1 double trapezoid MMI (DT-MMI) structure and use the mode propagation theory to model the DT-MMI structure. The analysis results show that DT-MMI weakens the influence of structural parameters on the number of interference points and reduces the sensitivity of output light intensity of the DT-MMI structure to structural parameters. The experimental results show that, when the injection current is 1.4 A and the base width and waist width are changed by 0.5 μm simultaneously, the output power of the laser with a rectangular MMI structure decreases to 86% of the device with unchanged base width and waist width, whereas that of the laser with DT-MMI decreases to 89%, which proves that the DT-MMI structure can reduce the parameter sensitivity of the device.