The present invention provides a method for modulating backlight sources for flat panel displays (FPD), which comprises: lowing steps: step 31: turning on a display screen; step 32: identifying whether the total number of the BLL groups provided on the backlight module is an odd number or an even number; step 33: turning on the one BLL group located at the center-most region of the backlight module while the total number of the BLL groups is an odd number; step 34: turning on the two BLL groups located at the center-most region of the screen while the total number of the BLL groups is an even number; step 35: turning on the two backlight groups located at the two outer side of the center turned-on backlight groups while turning off the center turned-on backlight groups, and similarly, progressing the turning-on and the turning-off from the center region to the two outer edge of the backlight module and then reverse-progressing respectively from the two edges to the center region, so as to complete a full cycle; step 36: determining whether the display screen is off; if so, the process proceeds to step (37); otherwise, the process goes to step (31); and step 37: ending the process.