The invention discloses a method for separating methane from oxygen-bearing coalbed gas. The methane is adsorbed from the oxygen-bearing coalbed gas comprising nitrogen and the methane. In the method for separating the methane from the oxygen-bearing coalbed gas, a treated activated carbon fiber is adopted for adsorbing the methane to realize separation from oxygen and the nitrogen by virtue of a hydrate method under the condition of introducing tetrahydrofuran. According to the method, the treated activated carbon fiber is adopted for obtaining an adsorbent for the methane in the oxygen-bearing coalbed gas under the condition of introducing the tetrahydrofuran to adsorb the methane by virtue of the hydrate method to realize separation of the nitrogen and the methane, and the methane concentration and recovery rate of product gas obtained by treatment with the method can be greatly increased.