Objective To explore the possible role of parvalbumin (PV)-positive interneuron in the pathogenesis of increased susceptibility to epileptic seizures in FMR1 gene knockout (FMR1 KO)mice. Methods Immunohistochemistry was employed to determine the expression of PV in CA1 and CA3 regions of the hippocampus, the striate cortex, the temporal auditory cortex and the piriform cortex of FVB strain FMR1 KO mice and wild type (WT) controls at the age of 2, 4 and 6 w. Western blotting was used to detect the level of PV in the cerebral cortex and hippocampus of the above mice. Results The numbers of PV-positive interneuron in CA1 and CA3 regions of the hippocampus, the striate cortex,the temporal auditory cortex and the piriform cortex of FMR1 KO mice at the age of 2 and 4 w were significantly decreased as compared with those in the age-matched WT mice (P<0.05). The level of PV in the cerebral cortex and hippocampus in FMR1 KO mice at the age of 2 and 4 w was also significantly decreased than that in the age-matched WT mice (P<0.05). Conclusion Decreased numbers of PV-positive interneuron and level of PV might induce the increased susceptibility to epileptic seizures inFMR1 KO mice.