NOVELTY - Production of synthesis natural gas comprises passing raw material gas through first heat exchange device (2), increasing temperature to 150-350 degrees C at volume ratio of 1:0.5-5:0-0.5:0-0.5, adding first mixed gas into first section of methanation reactor (9) to 450-750 degrees C first section product gas (10), taking first product gas to obtain first time period temperature of product gas at 250-400V by second heat exchange device, passing mixed gas through sixth heat exchange device (32) at 20-35 degrees C, and gas-liquid separating temperature at 20-80 degrees C to obtain product gas.    USE - Method for producing synthesis natural gas (claimed).    ADVANTAGE - The method improves energy comprehensive utilization efficiency.    DETAILED DESCRIPTION - Production of synthesis natural gas comprises:    (A) passing raw material gas through first heat exchange device (2), increasing temperature to 150-350 degrees C at volume ratio of 1:0.5-5:0-0.5:0-0.5, dividing into first stock of raw material gas (4), second stock of raw material gas (5), third stock of raw material gas (6) and fourth stock of raw material gas (7), connecting first stock of raw material gas with first steam (37), circulating gas after pressurizing at 250-400 degrees C to obtain first mixed gas (8), adding first mixed gas into first section of methanation reactor (9) to 450-750 degrees C first section product gas (10), and taking first product gas to obtain first time period temperature of product gas at 250-400V by second heat exchange device;    (B) dividing into recycle gas (13) and second section of first product gas (14), passing recycle gas (13) through third heat exchanging device (15) at 10-35 degrees C, passing circulating gas (16) through circulating compressor (17), entering circulating gas (18) through third heat exchange device, and increasing temperature to 250-350 degrees C of boosting the circulation gas (19);    (C) mixing raw material gas at 250-400 degrees C to obtain second mixed gas (20), passing into second section of methanation reactor to react at 450-700 degrees C, passing second section product gas through fourth heat exchange device, cooling product gas of second section, reducing temperature of second section of product gas by fifth heat exchange device, cooling to 20-40 degrees C to obtain temperature of second section of product gas, cooling second section of product gas (26), adding third mixed gas (27) into third section of methanation reactor at 30-55 degrees C to obtain third product gas (29), passing third section product gas through first heat exchange device, reducing temperature to 60-350 degrees C, and cooling third product gas; and    (D) cooling third product gas (30) and fourth stock of raw material gas at 6-20 degrees C of fourth mixed gas, passing mixed gas through sixth heat exchange device (32) at 20-35 degrees C, increasing temperature of mixed gas into fourth section of methanation reactor to react at 250-450 degrees C, and passing fourth section product gas through sixth heat exchange device and gas-liquid separating temperature at 20-80 degrees C to obtain product gas.    An INDEPENDENT CLAIM is included for device comprising first section of methanation reactor, second section of methanation reactor, third section of methanation reactor, fourth section of methanation reactor and thermal insulation fixed bed methanation reactor.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of the production of synthesis natural gas.    Heat exchange device (2)    First stock of raw material gas (4)    Second stock of raw material gas (5)    Third stock of raw material gas (6)    Fourth stock of raw material gas (7)    First mixed gas (8)    Methanation reactor (9)    First section product gas (10)    Recycle gas (13)    First product gas (14)    Third heat exchanging device (15)    Circulating gas (16,18, 19)    Circulating compressor (17)    Second mixed gas (20)    Second section of product gas (26)    Third mixed gas (27)    Third product gas (29)    Third product gas (30)    Sixth heat exchange device (32)    First steam (37)    Third steam (39)