To explore the influencing factors of the gestational diabetes mellitus (GDM) complicated with hypothyroidism of pregnant women, and to study their influence on the maternal and infant outcomes. Methods: The clinical data of 108 pregnant women with GDM complicated with hypothyroidism from January 2020 to January 2023 were collected in observation group, and the clinical data of 134 pregnant women with GDM only during the same period were collected in control group. The influencing factors of GDM complicated with hypothyroidism of the women and their influence on the maternal and infant outcomes were analyzed. Results: The proportions of the gravidity ≥3 times, the parity ≥3 times, the history of thyroid disease, the history of gestational hypertension and the family history of thyroid disease of the women in the observation group were significantly higher than those of the women in the control group (P<0.05). The levels of fasting blood glucose, creatine kinase, 2h postprandial blood glucose, creatine kinase isoenzyme, total cholesterol, uric acid, glycosylated hemoglobin and fibrinogen, and the thrombin time value of the women in the observation group were significantly higher than those of the women in the control group, but the prothrombin time of the women in the observation group was significantly lower (all P<0.05). The multiple gravidity and parity, the history of thyroid disease, the history of gestational hypertension, the history of family thyroid disease, the low value of prothrombin time and the high value of thrombin time of the pregnant women were the risk factors of their GDM complicated with hypothyroidism (P<0.05). The total incidence of the adverse maternal and infant outcomes (41.7%) of the women in the observation group was significantly higher than that (14.9%) of the women in the control group (P<0.05). Conclusion: The multiple gravidity and parity, the history of thyroid disease, the history of gestational hypertension and the history of family thyroid disease, and the low value of prothrombin time and the high value of thrombin time of the pregnant women are the risk factors of their GDM complicated with hypothyroidism, which may have influence on the adverse maternal and infant outcomes. It is suggested that the thyroid function of these pregnant women should be closely monitored, and the preventive and treatment measures should be taken for these women timely, so as to improve the maternal and infant outcomes.