A source driver and a method to reduce peak current of the source driver are provided. The source driver includes a latch circuit, a level shifter and a digital-to-analog converter (DAC) circuit. The latch circuit latches current bit-data. The latch circuit is coupled to an input terminal of the level shifter. The DAC circuit is coupled to an output terminal of the level shifter. When the current bit-data is not a complement of previous bit-data, the latch circuit selects and outputs the current bit-data to the input terminal of the level shifter, and the DAC circuit outputs a voltage corresponding to the output data of the level shifter. When the current bit-data is the complement of the previous bit-data, the latch circuit selects and outputs the previous bit-data to the input terminal of the level shifter, and the DAC circuit outputs a voltage corresponding to the current bit-data.