The present invention discloses an offset cancellation current mirror and method thereof. The offset cancellation current minor comprises a first current mirror, a second current minor, switches and resistors. The first current minor comprises two transistors and a capacitance, the capacitance is used to store an electrical potential difference when the switches are turned on in ways of connecting the first current mirror with the resistor. When the switches is turned off in ways of disconnecting the first current mirror with the resistor and connecting the first current mirror with the second current minor, the electrical potential difference stored in the capacitance is used to correct the difference of the two transistors due to manufacture process.