A display driving device and a method for driving a display are provided. The display driving device includes a host and a driving chip. The host transmits an image data and a synchronization signal. The driving chip receives the image data and the synchronization signal and drives a display panel to display frames. The driving chip includes a storage unit, a driving module, and a control circuit. The storage unit stores the image data. The driving module drives the display panel to display the frames according to the image data from the host and a timing generator frequency of the driving module. The control circuit detects a target frequency of the synchronization signal and the timing generator frequency of the driving module, compares the target frequency and the timing generator frequency, outputs an adjustment value according to the comparison result, and adjusts the timing generator frequency of driving module.