A head-mounted display device, comprising: an illumination system (350A, 350B, 350C), configured to provide an illumination beam, and comprising an aperture stop; a display device (130, 330A, 330B, 330C), configured to convert the illumination beam into an image beam, wherein the image beam is transmitted and projected to a projection target; a lens module (140, 340), configured to receive and project the image beam; and a waveguide system, configured to guide the image beam, and projecting the image beam to the projection target, wherein the waveguide system comprises a first waveguide element (110, 310) and a second waveguide element (120, 320), the image beam is projected to the projection target through the lens module (140, 340), the first waveguide element (110, 310) and the second waveguide element (120, 320), the image beam is converged to a first stop within the first waveguide element (110, 310), the first stop is located in the first waveguide element (110, 310), the image beam leaves the second waveguide element (120, 320), and is projected to a second stop out-side the second waveguide element (120, 320), the second stop is located at the projection target, characterized in that the illumination beam is converged to a third stop within the illumination system (350A, 350B, 350C), and the aperture stop is located at the third stop, and wherein the illumination system (350A, 350B, 350C) further comprises an illumination light source, a collimation lens set and a light uniforming element, wherein the illumination beam provided by the illumination light source is transmitted to the display device through the collimation lens set, the aperture stop and the light uniforming element in sequence. an illumination system (350A, 350B, 350C), configured to provide an illumination beam, and comprising an aperture stop; a display device (130, 330A, 330B, 330C), configured to convert the illumination beam into an image beam, wherein the image beam is transmitted and projected to a projection target; a lens module (140, 340), configured to receive and project the image beam; and a waveguide system, configured to guide the image beam, and projecting the image beam to the projection target, wherein the waveguide system comprises a first waveguide element (110, 310) and a second waveguide element (120, 320), the image beam is projected to the projection target through the lens module (140, 340), the first waveguide element (110, 310) and the second waveguide element (120, 320), the image beam is converged to a first stop within the first waveguide element (110, 310), the first stop is located in the first waveguide element (110, 310), the image beam leaves the second waveguide element (120, 320), and is projected to a second stop out-side the second waveguide element (120, 320), the second stop is located at the projection target, characterized in that the illumination beam is converged to a third stop within the illumination system (350A, 350B, 350C), and the aperture stop is located at the third stop, and wherein the illumination system (350A, 350B, 350C) further comprises an illumination light source, a collimation lens set and a light uniforming element, wherein the illumination beam provided by the illumination light source is transmitted to the display device through the collimation lens set, the aperture stop and the light uniforming element in sequence.