The invention relates to a backlight system and a microstructure reflector plate thereof, the backlight system comprises a light guide plate, a light source and a reflector plate, wherein the light guide plate is provided with a light inlet surface, a light outlet surface and a bottom surface which is opposite to the light outlet surface, the light source is arranged near the light inlet surface, the reflector plate is arranged near the bottom surface, and the reflector plate is equipped with a micro-reflection structure. Simultaneously, the invention also relates to a microstructure reflector plate, which is used in the backlight system for displaying of a passive lighting flat-panel, and is provided with a micro-reflection structure. By means of the above structure, light can be reflected by utilizing the reflection surface of the micro-reflection structure of the reflector plate, a light reflecting field can be modulated by changing the inclination angle of the reflection surface, the brightness value in an ideal vision field of the light guide plate can be further increased, therefore the design has flexibility and commonality, and can reduce or avoid using traditional prism sheets, thereby simplifying the device structure, increasing the optical energy usage, and reducing the cost.