The invention discloses a method and a device for adjusting a backlight value, relates to the technical field of display, and is used for solving the problem of brightness flickering caused by a conventional Local Dimming algorithm at a bright-dark junction, the method comprises the following steps: carrying out filling processing on a backlight setting matrix corresponding to an image to obtain afirst filling matrix; judging the backlight value of the backlight partition corresponding to the backlight setting matrix in the first filling matrix, and adjusting the backlight value needing to beadjusted according to the judgment result to obtain an adjusted backlight setting matrix; carrying out filling processing on the adjusted backlight setting matrix to obtain a second filling matrix; judging the backlight value of the backlight partition corresponding to the adjusted backlight setting matrix in the second filling matrix; according to the backlight adjusting method and device, the backlight setting matrix is subjected to smooth filtering processing, a more reasonable backlight value is obtained, and therefore the problem of brightness flickering is solved.