<p>To investigate the efficacy and mechanisms of fractional CO2 laser treatment for Vaginal Relaxation Syndrome (VRS) combined with recurrent bacterial vaginitis. Patients with VRS and recurrent bacterial vaginitis were randomly assigned to an intervention group (<i>n</i> = 60) receiving fractional CO2 laser therapy in addition to metronidazole, or a control group (<i>n</i> = 60) receiving metronidazole alone. Post-treatment assessments included vaginal relaxation, vaginal health index (VHI) scores, lactobacilli distribution, vaginal pH, recurrence rates, and the correlation between lactobacilli distribution and VHI. (1) Vaginal relaxation improved significantly in the intervention group compared to both pre-treatment and the control group (<i>P</i> = 0.000). (2) VHI scores and lactobacilli distribution improved in both groups post-treatment, with significantly higher scores in the intervention group (<i>P</i> = 0.000). (3) The intervention group exhibited a significantly lower vaginal pH compared to pre-treatment and the control group (<i>P</i> = 0.001). (4) Recurrence rates were significantly lower in the intervention group (8.33%) compared to the control group (36.67%) (<i>P</i> = 0.000). A strong positive correlation was found between lactobacilli distribution and VHI in the intervention group (<i>r</i> = 0.79, <i>P</i> &lt; 0.001). Fractional CO2 laser combined with conventional therapy improves VRS and recurrent bacterial vaginitis outcomes, reduces recurrence, and enhances vaginal microecology.</p><p><b>Trial registration</b>: Chinese Clinical Trial Registry, Registration number ChiCTR2400094125.</p>