Objective: To study the effects of hypothyroidism on pregnancy outcome and neonatal adverse outcomes in pregnant women with gestational diabetes mellitus. Methods: A total of 161 cases of late pregnant women who were treated in our hospital were selected from May 2014 to May 2015. The pregnancy with gestational diabetes mellitus (hypothyroidism group (group I, n=42), gestational diabetes and thyroid function in normal group (group II, n=73), gestational diabetes, 46 cases of hypothyroidism group (group III). OGTT test and thyroid function tests were conducted to examine the pregnancy outcome and the umbilical cord blood of newborns. Results: On three groups of pregnancy outcome and neonatal adverse outcomes were compared, group I gestational hypertension disease prevalence rate was 19.0%, far higher than that of group II 5.5% and group III 9.3%; group I prom incidence is 14.3%, postpartum hemorrhage incidence is 4.8%, neonatal asphyxia incidence rate was 4.8%, are higher than that of group II, III group the incidence and pregnancy induced hypertension, premature rupture of membranes, postpartum hemorrhage, neonatal asphyxia data difference had statistical significance (P<0.05), and placental abruption, premature birth, neonatal hypoglycemia occurred rate had no statistical significance (P>0.05). Conclusion: Hypothyroidism can increase the incidence of GDM in pregnant women with hypertension, premature rupture of membranes, postpartum hemorrhage and neonatal asphyxia, and improve the thyroid function of pregnant women in clinical practice to reduce the adverse pregnancy outcomes of pregnant women.