A source driver includes a first drive channel circuit, a voltage controller and a first programmable voltage buffer unit. The first drive channel circuit receives a first pixel data and a first reference voltage group, for driving the display device. The voltage controller receives a voltage command during a line data transmitting period, a horizontal blanking period or a vertical blanking period for generating a first reference voltage configuration data. The first programmable voltage buffer unit is coupled to the voltage controller and the first drive channel circuit, and receives the first reference voltage configuration data for applying the first reference voltage group to the first drive channel circuit. Furthermore, a method for driving a display device is also provided.