Melamine production is known to produce tail gas with a significant amount of CO2 and NH3. Ionic liquid as a green and excellent solvent is to be used for separating melamine tail gas. This paper aims to present a detailed multi-objective optimization (MOO) for the CO2/NH3 separation of the tail gas by ionic liquid (IL) in technical-energy-economic evaluation. Functional IL ([Bim][NTf2]) was selected, the ionic liquid-based process was designed, and process performances were investigated by process simulation and optimization. According to the optimization results, specific cases with different objective functions were chosen, and the relationship between key parameters was analyzed. The results showed that the ionic liquid-based technology could realize a better performance regarding the technical-energy-economic than the base case. Deeper analyses with the influence of operation parameters with evaluation index were carried out, thus providing support to the industrial application of the new separation technology.