The invention discloses a magnetic-stirring gas-rising internal circulation denitrification type methane anaerobic oxidation bacterium enrichment device and method. The device comprises a reactor body, a reaction vessel, a reactor cover plate, a flow guiding cylinder, an effluent biomass entrapping ring an aeration pipe, wherein the reactor body is divided into a gas rising region and a liquid falling region by the flow guiding cylinder, the gas rising region is located between the reaction vessel and the flow guiding cylinder, the effluent biomass entrapping ring is arranged at the upper part of the gas rising region, the aeration pipe is arranged at the bottom part of the gas rising region, the liquid falling region is located inside the flow guiding cylinder, a temperature probe is arranged at the upper part of the liquid falling region, a stirring magneton is arranged at the bottom part of the liquid falling region, and the stirring magneton and the temperature probe are controlled by a constant temperature magnetic stirrer. According to the invention, a gas-rising type reactor and a magnetic stirring reactor are ingeniously combined, thus the mass transfer area is enlarged, the transfer performance is enhanced, the enrichment efficiency is increased, the cyclic utilization of methane gas is realized, the utilization rate of methane is improved, and the discharge amount ofexhaust gas is reduced.