A calibration system adapted to calibrate a resistance of an electrical device having a lead wire comprises a resistance detector adapted to detect the resistance of the electrical device, a first container containing an etching solution adapted to etch the lead wire, and a heater configured to heat the electrical device. If a first resistance of the electrical device detected by the resistance detector at a first temperature is within a first predetermined range, the electrical device is heated with the heater to a second temperature higher than the first temperature. A second resistance of the electrical device is detected by the resistance detector at the second temperature. If the second resistance is beyond a second predetermined range, the lead wire is etched by the etching solution to adjust the resistance of the electrical device until the second resistance at the second temperature is within the second predetermined range.