C16/C18 alkyl amidoproyl trimethyl ammonium mono-methyl carbonate was synthesized via a high pressure process with tertiary amines and dimethyl carbonate, the chemical structure of which was confirmed using mass spectral fragmentation and FTIR spectroscopic analysis. In addition, several quaternary ammonium salts with new counterions X- (X= HCOO, CH3COO, CH3CH(OH)COO) were also synthesized by ion exchange reaction of methyl carbonate quaternary ammoniums with corresponding acids. The surface activities of these quaternary ammonium salts were studied. The results show that counterion chain length has effect on the surface tension.