A method for driving an LCD device includes displaying each picture with two frame images sequentially; the two frame images includes a first frame image and a second frame image; driving voltages for two adjacent sub-pixels in each of the frame images are different, and driving voltages in the first frame image and the second frame image for each of the sub-pixels are different; determining backlight brightness regulation signals for each of the backlight subareas; the backlight regulation signals are grouped signals, the number of the groups is identical to the number of types of the color sub-pixels; calculating an average color purity of a current picture area corresponding to each backlight subarea; determining whether the average color purity of each of the backlight subareas is within a preset range; if yes, performing a brightness regulation to a backlight source of the backlight subarea in each of the frame images of a next picture according to the backlight brightness regulation signal of the backlight subarea.