Abstract: The EI mass spectra of two kinds of fluoro-p-terphenyl liquid crystalline compounds (FTPLCCs) were analyzed by gas chromatogram-mass spectrometry （GC/MS）, and the fragmentation rules of FTPLCCs were summarized. The main fragmentation pathways of FTPLCCs are the loss of an alkyl from the molecular ions via benzyl cleavage. The fragmental ion at m/z 274 can be produced from some other bigger fragmental ions, which is contrary to the even electron rule. The position of fluorine atom has some influence on the fragmentation pathways of FTPLCCs. The relative abundances of the fragmental ions have obvious differences caused by the electron-withdrawing inductive effect of fluorine atom and resulting alternation of the conjugation degree of the terphenyl moieties.