1. A backlight control method, comprising steps of: inputting backlight adjusting information into a display apparatus through infrared remote control, touch control or sound control by a user, acquiring backlight information and writing the backlight information into a backlight register of a system on chip of the display apparatus; obtaining backlight adjusting data based on the backlight information in the backlight register; inputting a full high definition image signal into a field-programmable gate array of the display apparatus, which is configured to input an ultra high definition image information into a display screen of the display apparatus by the system on chip; sending the backlight adjusting data to a backlight control register of the field-programmable gate array, so that the backlight control register obtains a corresponding backlight control register value based on the backlight adjusting data and the display screen of the display apparatus displays the ultra high definition image information and the backlight adjusting information from the field-programmable gate array; and adjusting backlight according to the backlight control register value.