Abstract: Anisodamine shows activity as cholinoceptor blocking agent. Some new anisodamine derivatives were synthesized. To confirm the structures of those derivatives, their mass spectrometries were studied through electrospray ionization-ion trap mass spectrometer. The results indicated that anisodamine derivatives modified by benzyl, the quaternary ammonium chloride, could form a molecular-related ion M+35- and producted ions through elimination of methyl chloride or benzyl chloride in spectra of negative ion mode. In positive ion mode, ESI-MS spectra of three compounds all gave molecular-related ions M-35+. Their MS 2-4spectra gave the characteristic product ions which were also formed by the cleavage of C-N bond accompanied with breaking of HO-C, H-C or RCOO-C bonds of the quaternary ammonium cation of compound a-c.