A pump ring. The pump ring is suitable for a reaction chamber and capable for extracting gas from the reaction chamber in a uniform gas flow rate. The pump ring comprises a ring body and a top ring part located on the ring body. The top ring part is apart from an inner wall of the reaction chamber with a fixed distance. Therefore, a gas-extraction path composed of the reaction chamber, the ring body and the top ring part is unobstructed. Hence, the turbulence flow of the extracted gas can be efficiently suppressed and the problems of the accumulation of the impurities and reaction chamber contamination can be solved.