Abstract： Objective To observe the expression ofmicroRNA-134 (miR-134) in the mouse brain tissue with FMR1 gene knockout during the different development periods and its expression characteristic, and explore whether the deficiency of fragile X mental retardation protein (FMRP) can induce the changes of miR-134 transcription. Methods FVB strain male mice, including FMR1 gene knockout (KO, n=15) and their wild type (WT, n=15) counterparts were chosen in the experiment. The expressions of miR-134 in the brain tissues of these KO mice that were 0 d, 4 and 6 w old and the age-matched WT mice were detected by qRT-PCR. Results The transcriptional level of miR-134 in the brain tissue of KO mice had no significant difference as compared with that of age-matched WT mice (P＞0.05). The transcriptional levels of miR-134 in 6-w-old KO and WT mice were significantly decreased as compared with the newbom and 4-w-old same genotype mice (P＜0.05). Conclusion The absence of FMRP does not influence the transcription of miR-134 and the transcriptional level of miR-134 in the brain tissues maintains a high level during the developmental stage of the nervous system and gradually decreases to a low level after grow-up, demonstrating its important role in regulating the development of nervous system.