An X-ray image detection system includes a charge accumulation device, a switch device, a comparator device and an analog to digital converter. The charge accumulation device receives current produced by a pixel and converts the current to a voltage signal. The switch device has an input terminal, a first output terminal, and a second output terminal. The input terminal is connected to the charge accumulation device to receive the voltage signal. The comparator device is connected to the first output terminal for generating first or second indication signal according to the voltage signal. The analog to digital converter is connected to the second terminal. When the first indication signal is generated, the input terminal of the switch device is connected to the first output terminal. When the second indication signal is generated, the input terminal of the switch device is connected to the second output terminal.
