A method is for controlling an impedance of a via of a printed circuit board. The Via is connected with a trace and includes a drill hole, a pad and an anti-pad. The method includes steps of: building a math model; testing whether an impedance of the via matching with an impedance of the trace; analyzing the impedance of the via if passing the testing; and adjusting parameters of the pad, the anti-pad, and the drill hole if fails testing, and returning to the simulating step, till impedance matching achieved. The method which can efficiently keep signals integrality and increase signal transmission speed.