Calix[6]arenes often serve as molecular host in supramolecular chemistry, however, they show a conformation flexibility due to the inversion of the aromatic rings. It is important to control the structure flexibility of calix[6]arenes. In this work, a C3. symmetrical molecular receptor calix[6]TPA was synthesized and characterized via H NMR, “C NMR, ESI-MS, and X-ray structural analysis. Molecular recognitions of calix[6]TPA for small organic ammoniums were investigated with H NMR, and the inclusions of the straight chain ammoniums were reversiblly controlled by the acidity of the solution. The results indicate that the introduction of a tripodal N4-crypto cap is beneficial to rigidify the structure in a cone conform ation, the hydropho-bic cavity is an eficient receptor for organic guests, and the, reversible recognition of straight chain ammoniums can be potentially applied in separation of organic amines.