A voltage compensation circuit and a voltage compensation method are provided. The voltage compensation circuit detects the load current provided by a power supply, generates a load voltage according to the load current, and compares the load voltage with at least one reference voltage to generate a switch control signal. The voltage compensation circuit further drives the at least one switch according to the switch control signal, provides a compensation resistance value according to the at least one switch that is turned on, and provides a compensation voltage to the power supply, so that the power supply provides a precise output voltage.