The invention discloses a vehicle rear-view auxiliary system and a control method thereof. The vehicle rear-view auxiliary system comprises a rear-view unit, an image capturing unit and a processing unit, wherein the processing unit is electrically connected to the rear-view unit and the image capturing unit respectively; the processing unit is used for receiving a surrounding image acquired by the image capturing unit and displaying the surrounding image on the rear-view unit; the processing unit is also used for determining whether the surrounding image is clear; the processing unit controls the rear-view unit to switch to a reflection mode if the surrounding image is fuzzy; and the processing unit controls the rear-view unit to switch to a display mode if the surrounding image is clear. The vehicle rear-view auxiliary system and the control method thereof automatically switch the reflection mode and the display mode of a rear-view mirror according to the clarity of captured images, and are safe and reliable.