A dynamic control method for controlling backlight module of liquid crystal display (LCD) comprises steps of: receiving a frame data which is transferred to the LCD and consists a plurality of raw grayscale level; processing a statistical analysis for distribution of the plurality of raw grayscale level; and transferring a plurality of corrected grayscale level which is resulted from the statistical analysis corresponding to the raw grayscale level to the backlight control unit and a data modification simultaneously, wherein the backlight control unit uses the plurality of corrected grayscale level to modify brightness of backlight module and the data modification uses the plurality of corrected grayscale level to compare with the plurality of raw grayscale level for accurate display performance, so that the electrical power consumption is reduced and image quality is enhanced.