Purpose : Foot muscle strengthening exercises, including short-foot exercise, are effective in improving foot alignment and arch height in individuals with flexible flatfoot. However, given the limited methodological quality of domestic studies, these findings should be interpreted with caution, and further high-quality RCTs are needed to strengthen clinical evidence. Methods : A systematic search of domestic databases identified 92 studies, with 17 clinical trials meeting PICO-SD inclusion criteria (patient characteristics, intervention, comparison, outcome, and study design). Outcomes included foot arch height and foot alignment angle. First, quality was assessed by using the PEDro scale for 10 randomized controlled trials (RCTs) and RoBANS 2.0 for 7 non-RCTs. Second, effects were calculated as Hedges’ g (standardized mean difference), with multiple intervention arms treated as separate units. Third, cluster-robust variance estimation (CRVE) addressed dependency violations. Fourth, a random-effects model was applied due to high heterogeneity. Fifth, publication bias was assessed with Egger’s regression and trim-and-fill methods. Finally, sensitivity and meta-regression analyses explored sample size, treatment duration, and study design effects. Results : Foot muscle strengthening exercises showed sizeable effects in foot arch height (Hedges’ g= -1.42, 95 % CI: -2.01 to -0.83, k= 18) and foot alignment angle (Hedges’ g= -1.23, 95 % CI: -2.11 to -0.34, k= 15). The subgroup analysis indicated a significant effect on the study design (RCT vs. non-RCT) on foot alignment angle (p= .014), but not on foot arch height. The meta-regression identified treatment duration as a significant moderator in foot arch height (p= .028). Publication bias was detected (Egger’s test: p=.000 for foot arch height, p= .000 for foot alignment angle), but trim-and-fill adjustments confirmed robust effects. Furthermore, high heterogeneity was observed (I²= 79.80 % for foot arch height, I²= 91.15 % for foot alignment angle). Conclusion : The findings in this study indicate that foot muscle strengthening exercise interventions have a positive effect on flexible flatfoot. However, due to the low quality of previous studies, the results of our study must be interpreted cautiously.