Plasma Chemical Vapor Deposition ( PCVD ) is an important application in making optical fiber core rod. The resonator is the key part for PCVD application. But the existing resonator have several serious disadvantages: its working is not stable; the size of deposited substrate tube is small(Ø31mm); the deposition rate is low(2.5g/min) and the deposition effect is unsymmetrical; the fabrication of the resonator is very difficult and expensive. Therefore, a new type of resonator, a cylinder resonator, is designed to overcome the above disadvantages. The cylinder resonator supports bigger substrate tube (Max Ø60mm) and higher deposition rate(3.2g/min) than existing ones, while its working is also more stable. Since the structure is more simple, the fabrication is easier and cheaper. The corresponding microwave theoretical method of the new resonator designing is also introduced with the necessary computer simulation, as well as test running. And TE111 mode microwave is the Fundamental Mode of the cylinder resonator. The cylinder resonator has been applied in normal production for 4 years, which is better for bigger size core rod making, improving the optical fiber quality and saving cost. It is estimated, after modification with the cylinder resonator and 10kW microwave generator, a PCVD lathe can yield 30% more rods than before.