A gas-flow control method for a plasma apparatus is provided. The gas-flow control method includes mounting a first adjusting mechanism on a gas-distribution plate. The gas-distribution plate includes a number of exhaust openings, and the exhaust openings in a first area of the gas-distribution plate are masked by the first adjusting mechanism. The gas-flow control method also includes exhausting a gas from the exhaust openings in a first unmasked area of the gas-distribution plate, and the gas passing through the first adjusting mechanism into a plasma chamber. The gas-flow control method further includes generating an electric field to excite the gas in the plasma chamber into plasma.