NOVELTY - An ammonia recycling system comprises heat exchangers; drying dehydrator which is connected to one heat exchanger and waste gas of synthetic ammonia after hydrogen is extracted; expanding machine set which is connected with methane rectifying tower; argon rectifying tower having evaporating heat exchanger; argon storing tank; synthetic ammonia production line; methane rectifying tower comprising evaporating heat exchanger; and compressor machine set to which one heat exchanger is connected.    USE - A system for recycling synthetic ammonia and separating waste gas.    ADVANTAGE - The system efficiently utilizes resources and does not pollute the environment.    DETAILED DESCRIPTION - An ammonia recycling system comprises heat exchangers, drying dehydrator, expanding machine set, argon rectifying tower, argon storing tank, synthetic ammonia production line, methane rectifying tower comprising evaporating heat exchanger, and compressor machine set. The dehydrator has outlet end that is connected with lower end of first heat exchanger and inlet end that is connected with waste gas of synthetic ammonia after hydrogen is extracted. The expanding machine set has inlet that is connected with upper end of the first heat exchanger, and outlet that is connected with methane rectifying tower and right end of third heat exchangers. The argon rectifying tower is connected to two heat exchangers, and has evaporating heat exchanger. A left end of the first heat exchanger is connected with argon storing tank and synthetic ammonia production line. A lower end and a left end of the fourth heat exchanger are respectively connected with outlet and inlet of compressor machine set. The evaporating heat exchanger of the methane rectifying tower has one end connected with upper end of fourth heat exchanger and another end connected with other end of the third heat exchanger. The expanding machine set, methane rectifying tower, argon rectifying tower, expanding machine set and heat exchanger are in cool environment.