A pixel unit for driving an organic light emitting diode (OLED) is disclosed. The pixel unit includes a driving transistor, a compensating capacitor, a selecting switch module, a power switch and a configuration switch. One terminal of the compensating capacitor is coupled to a gate of the driving transistor. The selecting switch module provides the ground voltage or the compensating voltage to the other terminal of the compensating capacitor according to a first control signal. The power switch is coupled between a power voltage and a drain of the driving transistor and is controlled by a second control signal. The configuration switch receives the first control signal for controlling a connecting configuration of the driving transistor. The pixel unit is driven according to the first and the second control signals for compensating threshold voltage shifting of the OLED and the driving transistor.