AIM: To investigate the effects of hydrogen-rich saline (HRS) on microglia activation and Sirtuin type 1 (Sirt1) in rats with N-methyl-N-nitrosourea (MNU)-induced retinitis pigmentosa (RP). METHODS: Rats were divided into norm (N) group, model (M) group and HRS (H) group. Rats in M and H groups were given saline and HRS respectively prior to and after administration of MNU. At one day (d1) and d3 afterwards, electroretinogram and histological examination were performed to confirm the effects of HRS on retinal function and structure of MNU-induced RP. Immunofluorescence staining of anti-ionized calcium-binding adapter molecule 1 (Iba1), a maker of microglia cells, was performed, with quantitative real-time polymerase chain reaction (qRT-PCR) for its mRNA quantification. Moreover, Sirt1 mRNA and protein expression in the retinas were detected by Western blot and qRT-PCR. RESULTS: HRS preserved the retinal function and mitigated the reduction of photoreceptor degeneration in MNU-treated retinas. The presence of microglia cells was somewhat more obvious in H group than that in M group at d1. HRS suppressed the further activation of microglia cells, with the number of microglia cells less than that of M group at d3. Results of qRT-PCR of Iba1 were consistent with those of immunofluorescence staining, with the mRNA expression of Iba1 in H group more intensive than that of M group at d1 (P<0.05), while less than that of M group at d3 (P<0.05). Furthermore, the Sirt1 mRNA and protein expression decreased after MNU administration, while HRS mitigated the MNU-induced downregulation of Sirt1. CONCLUSION: HRS can effectively keep microglia activation induced by MNU to an appropriate extent, while upregulate Sirt1 in MNU-induced RP.