A display control device includes a detector, a frequency adjusting signal generator, a clock generator and an output timing generator. The detector compares an input field reference signal with an output field reference signal to determine a time difference signal. The frequency adjusting signal generator outputs a frequency adjusting signal. The clock generator outputs a clock according to the frequency adjusting signal. The output timing generator generates an output field synchronization signal according to the clock. The clock generator adjusts the frequency of the clock according to the frequency adjusting signal.