MgCl2-loaded activated carbons were prepared by ultrasonic impregnation method for the application in ammonia enrichment or ammonia decomposition process. Anhydrous magnesium chloride (MgCl2) was selected as an active promoter for ammonia adsorption, and cyclic adsorption performance was comparatively analyzed according to MgCl2 loading (3-20wt% in Mg basis). The physical and chemical properties of the adsorbents were analyzed by TGA, BET, SEM, EDX, and NH3-TPD. The adsorption and desorption characteristics were analyzed via temperature swing (TSA), pressure swing (PSA), and pressure-temperature swing (PTSA) mode breakthrough tests. It was confirmed that 10 wt% Mg loaded adsorbent (AC-Mg(10)) among the prepared sorbents showed the best performance in the cyclic adsorption process, showing the ammonia capacity of 2.461mmol NH3/g in TSA mode operation. Even though the capacity was lower (around 1mmol NH3/g) in PSA mode, the PSA mode operation was very attractive due to its stable and convenient operation conditions. The ammonia desorption temperature for TSA and PTSA mode operation was determined based on the van’t Hoff equation which define equilibrium pressure and temperature of three sequential reaction of MgCl2 with ammonia. PTSA mode breakthrough test showed the excellent performance even with a mild increase of temperature for desorption. AC-Mg(10) showed a remarkable adsorption capacity of 4.062mmol NH3/g in the first cycle at an elevated pressure. When a mild temperature, 393 K, was applied for desorption, the cyclic adsorption capacity of 2.769mmol NH3/g was achieved, which exceeded the one in TSA mode operation.