The invention relates to a recycling method for 
phosgene in 
tail gas generated in 
calorescence reaction for synthesizing normal-
butyl isocyanate. The recycling method comprises the steps of continuously cooling and absorbing the 
tail gas generated in the 
calorescence reaction for synthesizing the normal-
butyl isocyanate through a low temperature 
solvent, and condensing the 
tail gas through a condenser, wherein the non-condensing gas directly enters a tail gas 
processing system; preparing normal-butyl 
acyl chloride from the 
solvent containing the 
phosgene with certain quality concentration through cold light reaction, metering the 
phosgene-containing 
solvent, shifting the solvent into a cold light kettle, dropwise adding n-
butylamine at -8 DEG C to -2 DEG C, after the dropwise adding, keeping the temperature for 1 hour so as to obtain the n-
butylamine acyl chloride; and resolving the n-
butylamine acyl chloride in a 
calorescence reaction kettle to obtain the normal-
butyl isocyanate. The method provided by the invention has the advantages that the phosgene is utilized to the greatest extent, the load of the tail gas generated in the normal-butyl 
isocyanate calorescence reaction in a tail gas 
processing system and the alkali charge during tail gas 
processing are reduced, the production cost of the product is reduced, and the purpose of saving and recycling resources is achieved.