A multi-channel integrator is provided. The multi-channel integrator includes an integrator and a plurality of channels. Each of the channels includes an input selector and a unit-gain amplifier. The input selector has a common terminal, a first selecting terminal and a second selecting terminal. The input selector selectively electrically connects the common terminal to the first selecting terminal or to the second selecting terminal. The first selecting terminal of the input selector is coupled to an input terminal of the integrator. An input terminal of the unit-gain amplifier is coupled to the second selecting terminal of the input selector.