A backlight module and a driving method thereof are provided. The driving method includes following steps: first obtaining backlight data with N bits of data corresponding to each backlight unit in a current frame; then dividing time required by each backlight unit in the current frame to obtain N subfields with different durations; and finally outputting the N subfields of each backlight unit in a preset order, and controlling a scan line corresponding to the backlight unit to perform at least two scans in a first subfield, and a time interval between adjacent scans is less than a second threshold.