The invention belongs to the field of environmental protection, and relates to a method and a system for realizing efficient wastewater treatment and waste methane gas oxidation together via an artificial wetland, wherein a vertical flow artificial wetland with a good oxygen environment is selected by the system. The system comprises a water distribution matrix layer (5) and an artificial wetland aeration reaction bed (7), wherein a water distributor (4) connected with a sewage inlet pipe (1) is arranged in the water distribution matrix layer (5); wetland plants (3) are planted in the water distribution matrix layer (5); a water distribution room (9) with uniformly-distributed aeration heads (4) and an artificial wetland water collecting pipe (12) are arranged at the bottom of the artificial wetland aeration reaction bed (7); the water distribution room (9) is connected with a low-concentration methane gas inlet pipe (2); and an artificial wetland water outlet pipe (10) with a water sealing device (11) is arranged at the outlet of the artificial wetland water collecting pipe (12). In order to solve the problems that the demand of ecological treatment oxygen for a large amount of high-concentration wastewater in a livestock and poultry farm cannot be satisfied easily while the waste gas containing low-concentration methane is discharged at random to generate the greenhouse effect, the wastewater treatment and the waste gas treatment of the livestock and poultry farm are efficiently coupled, thereby providing the efficient and low-consumption method and system for realizing the efficient wastewater treatment and the waste methane gas oxidation together via the artificial wetland.