All-electron ab initio calculations of acetylcholine (Ach) ion have been carried out at the Hartree-Fock and the second order Moller-Plesset perturbation theory MP2 levels using 6-31G* basis set. Two stable conformations of gauche and trans forms of Ach have been found. It was found that after zero-point vibrational energy ZPVE corrections, at the Hartree-Fock level the gauche form is 0.24 kJ•mol-1 more stable than the trans, but at MP2 level the trans is 2.07kJ•mol-1 more stable than the gauche. The Harmonic vibrational frequencies have been computed at HF/6-31G* level. The Molecular Electrostatic Potentials, MEP contour maps of two conformations of the Ach based on MP2 wavefunctions are shown in this article.