Abstract: In the chemical imitation study of the one carbon unit transfer manner of tetrahydrofolate coenzyme, we designed and synthesized a series of 1,2,3-trisubstituted imidazolinium salts (1 and 2) serving as tetrahydrofolate coenzyme models. Their properties and the abilities of transferring one carbon unit were studied. Their structures were proved by ¹HNMR,¹³ CNMR,IR,elementary analysis etc. Here the mass spectral behavior were reported. In the mass spectra, we found that the peak m/z=137(I⁺) and the organic cation(A)peak present in all experiments in stead of the molecular ion peak. Compounds 1 and 2 have similar fragmentation pattern. The organic cations could lose one of the substituents linked to nitrogen atoms and reserve the ring to give out D, E, F fragment ions. More important is their imidazolinium rings splitted in the similar manner: the bonds C²-N³ and C⁵-N¹ or C²-N³ and C⁴-C⁵ brokedown and produced G and H fragments. The relative abundances were high, some were the base peak and others were the second main peaks. Because of the different substituents, the imidazolinium rings have different stability. A peaks of compound 2 were high and were the base peaks (expect 2d), the E,F peaks were low or none. But for compound 1,the A peaks were low and E,F peaks were high. In the mass spectra of 1c,1d,1e appeared C peaks (3 units less than A). This was a special rupture manner.