Objective:To investigate the impact of excessive fluoride exposure on the expression profile of microRNA (miRNA) in mouse testes, and elucidate the reproductive toxicity mechanism of fluoride.Methods:A total of 24 8-week-old C57BL/6J male mice weighing (23 ± 1) g were randomly divided into a control group [0 mg/L sodium fluoride (NaF)] and a fluoride exposure group (50 mg/L NaF) using a random number table method, with 12 mice in each group. After 90 days of treatment, the mice were anesthetized and euthanized. Sperm samples were collected to assess their quantity, viability, and deformity rate. Additionally, testicular tissue was stained with hematoxylin-eosin (HE). RNA was extracted from testicular tissue, and high-throughput sequencing technology was employed to analyze the effect of fluoride on the expression profile of mouse testicular miRNA. Deferentially expressed miRNA was screened and its target genes were predicted, and functional annotation and pathway enrichment analysis were performed. Real-time fluorescence quantitative PCR (qRT-PCR) was used to verify the expression level of deferentially expressed miRNA.Results:Compared with the control group [number of sperm: (11.30 ± 2.52) × 10 6/ml; viability rate: (90.07 ± 4.34)%; deformity rate: (15.49 ± 3.25)%], the number of sperm of mice exposed to fluoride [(9.01 ± 2.25) × 10 6/ml] and the viability rate [(84.34 ± 4.21)%] decreased ( P = 0.041, 0.003), while deformity rate [(22.36 ± 6.51)%] increased ( P = 0.003). Furthermore, in the fluoride exposure group, the interstitial distance of testis increased, the number of sperm in the spermatogenic tubule decreased, and the cell arrangement was disordered. Through sequencing, 34 deferentially expressed miRNAs were identified in the testes of mice exposed to fluoride. According to qRT-PCR verification, compared with the control group, the expression levels of mmu-miR-29b-1-5p ( P < 0.001), mmu-miR-196a-5p ( P = 0.002), and mmu-miR-196b-5p ( P = 0.031) in the testes of mice exposed to fluoride were significantly increased, and the expression levels of mmu-let-7a-2-3p ( P < 0.001) and mmu-miR-466n-3p ( P = 0.018) were significantly decreased, consistent with the sequencing results. By KEGG enrichment of deferentially expressed miRNA target genes, it was found that fluoride exposure could change the axon guidance signal pathway, olfactory transduction pathway, neuroactive ligand-receptor interaction pathway, and lysosome signal pathway, etc., in mouse testes. Conclusions:Fluoride exposure may induce testicular injury by altering the expression profile of miRNA in the testes and by mediating the post-transcriptional regulatory signal pathway. Testicular miRNA may be a potential biomarker of fluoride reproductive toxicity, which may provide a new idea and perspective for exploring the mechanism of fluoride poisoning.