We systematically investigate the binding nature of CB[7] towards 20 amino acids in both neutral (AAs) and protonated (AAs⁺) states by quantum chemistry methods. The result indicates molecular recognition process are enthalpy-driven. Among AAs, Arg and Asn shows the largest binding strength to CB[7], and for AAs⁺, Gln⁺ and Asn⁺ bind to CB[7] the strongest. The binding strength of protonated CB[7]/AA⁺ is much stronger than that of neutral CB[7]/AA counterpart, due to the introduction of ion-dipole interaction and the increase number and strength of hydrogen bonds. Energy decomposition analysis (EDA) indicates that electrostatic interactions play major roles in both CB[7]/AAs and CB[7]/AAs⁺ complexes. Moreover, we analyzed the dependence of binding strength on single AA volume and dipole moment. This study is benefit for providing valuable information in predicting the recognition sites for sequence-based peptide or protein by CB[7] and rationally designing synthetic host molecule for specific peptide or protein recognition.