A series of semi-perfluorinated ferroelectric liquid crystals, 5-(n-perfluoro alkyl)alkyloxy-2-[p-(2-fluorooctyloxy)phenyl]pyrimidines, was synthesized and their mesomorphic properties investigated. Compared with non-fluorinated analogue chiral smectic C phase is strongly enhanced. All of the compounds showed chiral smectic C phase enantiotropically. As fluorination extent of the achiral tail increased, tilt angle, spontaneous polarization and response time increased. Especially, when the length of the achiral tail is seven and fluorination extent is 60%, chiral smectic C phase is so stable that smectic A phase completely disappeared. What’s more, its spontaneous polarization is more than 300nC.cm(-2). All the compounds showed little temperature dependence of response time.