Introduction: Exercise showed some potential in preventing gestational diabetes mellitus. However, the results remained controversial. We conducted a systematic review and meta-analysis to evaluate the impact of exercise during pregnancy on gestational diabetes mellitus. Methods: PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases were systematically searched. Randomized controlled trials (RCTs) assessing the influence of exercise during pregnancy on gestational diabetes mellitus were included. Two investigators independently searched articles, extracted data, and assessed the quality of included studies. The primary outcome was the incidence of gestational diabetes mellitus. Meta-analysis was performed using random-effect model. Results: Six RCTs involving 2164 patients were included in the meta-analysis. Compared with control intervention, exercise intervention was associated with significantly decreased incidence of gestational diabetes mellitus (Std. mean difference = 0.59; 95%CI = 0.39-.88; p = .01), but had no effect on gestational age at birth (Std. mean difference = -0.03; 95%CI = -0.12 to 0.07; p = .60), the number of preterm birth (OR = 0.85; 95%CI = 0.43-1.66; p = .63), glucose 2-h post-OGTT (Std. mean difference = -1.02; 95%CI = -2.75 to 0.71; p = .25), birth weight (Std. mean difference = -0.13; 95%CI = -0.26 to 0.01; p = .06), and Apgar score less than 7 (OR = .78; 95%CI = 0.21-2.91; p = .71). Conclusions: Compared to control intervention, exercise intervention could significantly decrease the risk of gestational diabetes mellitus, but showed no impact on gestational age at birth, preterm birth, glucose 2-h post-OGTT, birth weight, and Apgar score less than 7. Keywords: Exercise; gestational diabetes mellitus; incidence of gestational diabetes; meta-analysis; systematic review.