The investigation of the host-guest complex formations between cyclophane (TGDMAP) (1) as a host and L-acidic amino acids such as L-glutamic acid (Glu) and L-aspartic acid (Asp) as guests was carried out using fast atom bombardment (FAB), electrospray ionization (ESI) and cold-spray ionization (CSI) mass spectrometry (MS). The stability constant (K(s)) values obtained by the three different MS methods almost agreed. However, the complex ion peaks of a novel cyclophane (CPCn) (2) with Glu and Asp were not observed in FAB-MS. Then, these host-guest complex formations by use of CSI-MS and ESI-MS was examined, as the results, these complex ion peaks were observed clearly and the measurement values by the two MS methods are mostly in agreement. It was concluded that ESI-MS and CSI-MS are available for the determination of K(s) value as well as FAB-MS.