Abstract: An atmospheric-pressure plasma reactor comprising a first electrode, a second electrode and a power generation unit. The first electrode and the second electrode respectively have a first opening and a second opening corresponding to each other. Disposed inside the first electrode is a gas-in space, which communicates with the first opening. Moreover, the power generation unit is coupled to the first electrode to provide the first electrode with AC power. The second electrode is grounded. The plasma process by the atmospheric-pressure plasma reactor is capable of forming high-uniformity thin film on a substrate.