Micro-LED display technology is regarded as the most promising next-generation display technology due to its advantages such as high brightness, high resolution, and high contrast. The development and application of technologies such as 3D display, medical detection, information encryption, visible light communication, efficient liquid crystal backlight display, polarized microscopy, and sensing have introduced new requirements for Micro-LEDs to achieve high extinction ratio polarized light output. To realize the design of a miniaturized red-light Micro-LED device capable of emitting linearly polarized light, this study integrates subwavelength metal gratings on the surface of AlGaInP-based red-light Micro-LEDs and employs the finite-difference time-domain (FDTD) method to conduct theoretical analysis and structural optimization of the metal gratings. The results demonstrate that by optimizing the grating parameters and the thickness of the dielectric layer, a red-light Micro-LED with a chip size of 50 μm achieves an extinction ratio of 26 dB, enabling high extinction ratio linearly polarized light output. The AlGaInP-based linearly polarized Micro-LED designed in this study exhibits significant potential for applications in the field of 3D Micro-LED displays.