NOVELTY - The method comprises: in the method of synthesizing an ammonia gas, introducing a semi-water gas with 40 degrees C from an energy source section into a spraying tower of a cooling tower; introducing into a compressor of a first compression section; pumping freeze water with 10-20 degrees C from an ion membrane caustic soda section to a top of the spraying tower of the cooling tower by a freeze water pump for exchanging heat with the semi-water gas; and cooling the semi-water gas to below 33 degrees C and then introducing into the compressor of the first compression section.    USE - The method is useful for recycling cold energy for improving yield of synthesis ammonia.    ADVANTAGE - The method recycles cold energy with reduced energy consumption.    DETAILED DESCRIPTION - The method comprises: in the method of synthesizing an ammonia gas, introducing a semi-water gas with 40 degrees C from an energy source section into a spraying tower of a cooling tower; introducing into a compressor of a first compression section; pumping freeze water with 10-20 degrees C from an ion membrane caustic soda section to a top of the spraying tower of the cooling tower by a freeze water pump for exchanging heat with the semi-water gas; cooling the semi-water gas to below 33 degrees C and then introducing into the compressor of the first compression section; and pumping the freeze water out of the bottom of the spraying tower to an ammonia cooler by a water recovering pump for cooling to 12-13 degrees C, and cooling the ammonia gas of the ion membrane caustic soda thus improving the yield of the synthesis ammonia while recycling the cold energy. A temperature of the semi-water gas emerging from the energy section is 36-40 degrees C, and the temperature of the freeze water exiting from the ion membrane caustic soda section, before exchanging heat with the semi-water gas, is 15 degrees C. The spraying tower of the cooling tower is an empty tower, and uses atomizing spray nozzles. A filter device such as a filter screen of 70-90 meshes is mounted at an inlet of the freeze water pump. The pressure at an outlet of the freeze water pump is 0.35-0.45 MPa. The water recovering pump is a centrifugal pump. An INDEPENDENT CLAIM is included for a method of improving yield of synthesis ammonia.    DESCRIPTION OF DRAWING(S) - The figure shows a flow chart of a method for recycling cold energy (Drawing includes non-English language text).