A method of calibrating an impedance-matching 
current sensor (IMCS) is provided. The IMCS has an equivalent sensing impedance and is connected in parallel to an object under test. The method includes steps of: using an alternating-current (AC) 
current source to provide a first 
AC current flowing through the object under test and provide a second 
AC current flowing through the IMCS; designing the equivalent sensing impedance to make the first 
AC current much greater than the second AC current; proportionally converting the second AC current into a sense 
voltage; and adjusting a magnitude of the sense 
voltage to be proportional to a magnitude of the first AC current. Accordingly, it is to significantly overcome problems of unreliability and 
instability of the DC-to-DC conversion 
system caused by temperature, aging, 
DC bias variation, or parasitic effect, thus maintaining correct sensed results of the 
current sensor in 
transient response optimization.