Objective To explore the correlation between serum homocysteine (Hcy) level and adverse pregnancy outcome in patients with gestational diabetes mellitus (GDM).Methods A total of 65 GDM patients who visited Benxi Central Hospital from January 2018 to January 2020 were selected as study subjects.Patients were followed up until delivery, and divided into adverse pregnancy outcome group (n=13) and good pregnancy outcome group (n=52) according to pregnancy outcomes.Compare the laboratory indexes of the two groups. Pearson correlation was used to analyze the correlation between serum glycosylated hemoglobin (HbA1c), fasting blood glucose (FBG) and Hcy in GDM patients.Logistic regression was used to analyze the relationship between serum HbA1c, Hcy, FBG and adverse pregnancy outcomes.Results Adverse pregnancy outcomes occurred in 13 patients.The levels of serum HbA1c, FBG and Hcy in the adverse pregnancy outcome group were higher than those in the good pregnancy outcome group, the differences were statistically significant (P＜0.05). Pearson correlation analysis showed that serum HbA1c, FBG and Hcy levels in GDM patients were positively correlated (r＞0, P＜0.01). Logistic regression analysis showed that high expression of serum HbA1c (β=1.059, OR=2.883, 95%CI=1.255-6.626), Hcy (β=0.896, OR=2.451, 95%CI=1.491-4.028), FBG (β=0.437,OR=1.548, 95%CI=1.122-2.136) in patients with GDM were risk factors for adverse pregnancy outcomes (P＜0.05).Conclusion HbA1c level of GDM patients is closely related to FBG level and Hcy level.The high expression of serum Hcy, FBG and HbA1c has a certain correlation with the incidence of adverse pregnancy outcomes in GDM patients.In clinics, the expression of serum Hcy, FBG and HbA1c levels in GDM patients can be used to predict the risk of adverse pregnancy outcomes and guide risk assessment and therapeutic intervention.