The invention relates to a method for recovering ammonia from ammonia-containing gas based on ionic liquid, which can solve the problems that a solvent is easy to volatilize, the energy consumption is high, the volume is small, wastewater is discharged and the like in the conventional method for recovering ammonia from ammonia-containing gas through water absorption. An absorption device recovers the ammonia from the ammonia-containing gas by taking the ionic liquid or a composite solvent as an absorbent; and the method comprises the following steps of: desorbing most noncondensable gas from ammonia-containing rich liquid through single stage or multiple stages of flash evaporation; and further performing flash evaporation to recover ammonia from the absorbent, and making the desorbed ionic liquid absorbent subjected to pressurization and temperature reduction enter the absorption device to circularly absorb the ammonia in the ammonia-containing gas. The recovery rate of ammonia is over 95 percent; and the process has the characteristics of environmental friendliness, low energy consumption, simple equipment, convenience of operation and the like.