A gamma voltage generator adapted in a source driver and a source driver adapted in a display panel are provided. The source driver comprises a DAC and a gamma voltage generator comprising a first and a second arithmetic circuit and a gamma voltage string. The first arithmetic circuit receives a first gamma reference voltage and at least one first tuning voltage to supply a first reference voltage. The second arithmetic circuit receives a second gamma reference voltage and at least one second tuning voltage to supply a second reference voltage. The gamma resistor string has two ends coupled to the first and the second arithmetic circuits to receive the first and the second reference voltages respectively to generate a plurality of gamma voltages. The DAC receives digital pixel data and the gamma voltages to generate a plurality of driving voltages to a pixel array of the display panel.