An integrator circuit is provided in the present invention, which utilizes a first capacitor and a first switching unit to sample an input signal and carries out distribution of charges between the first capacitor and a second capacitor. The second capacitor is larger than the first capacitor in capacitance. The integrator circuit transmits the charges stored in the second capacitor to a node of the first capacitor which is coupled to a ground previously. Accordingly, a direct current voltage level of the first capacitor may increase, facilitating an increase in a direct current voltage level at the second capacitor. Thereby, the accuracy and linearity of the integrator circuit may improve.