The invention discloses a methane purification system and a methane purification technology thereof, solving problems of high investment cost, high operation cost, high fault rate and low purification purity of a conventional system. The system comprises an anaerobic tank (1), a particle filter (2), a drying tower (3), a desulfurizing tower (4), a gasometer (5), a steam-water separation device (6), a low-pressure methane compressor (7), an interception type prefilter (8), a refrigeration drying machine (9), an agglomeration type filter (10), an oil-water separation filter (11), a precise ultimate filter (12), a heater (13), a first CO2/CH4 efficient separation membrane (14), a second CO2/CH4 efficient separation membrane (19) and a methane storage tank (20), wherein a methane-enrichment port (15) of the first CO2/CH4 efficient separation membrane (14) is communicated with a carbon dioxide purification device (16), and a carbon dioxide storage tank (17) is connected with the carbon dioxide purification device (16). The purification technology has high purification rate; and the whole set of technology can realize full-automatic operation.