The present invention provides LED voltage adjustment device and drive system thereof. The device includes PI regulator, with negative terminal connected to negative terminal of LED light bar to receive negative terminal voltage of light bar and positive terminal of PI regulator being for receiving reference voltage; integrator, for performing integral on output signal of PI regulator; a subtractor, with positive input terminal receiving output signal from PI regulator and negative terminal receiving overcurrent protection detection voltage from boost converter for driving light bar, and subtracting overcurrent protection detection voltage from output signal of PI regulator; comparator, with positive terminal receiving output signal from integrator and negative terminal receiving output signal from subtractor; and integrated circuit (IC) module, for receiving output signal from comparator and based on received output signal to control a control signal to conduct or cut off switch transistor of boost converter.