Objective:To study the effect of one-day outpatient intervention on gestational diabetes mellitus (GDM) patients,and to explore the pregnancy outcome relevant to GDM patients and their fetus.Methods:The GDM patients were divided into two groups according to their own intention to the one-day outpatient.According to systematic sampling method,we chose 200 GDM patients from the above 2 groups,respectively.The 200 GDM patients in the control group were matched the observation group with the age and gestational age,then the pregnancy outcome was tracked.Results:The control level and success rate for the two hours blood sugar after breakfast and hemoglobin A1c (HbA1c) in the observation group were better than those in the control group (P<0.001).The maternal complication rate (46.50%) and neonatal complication rate (21.50%) in the observation group were lower than those in the control group (71.50%,41.50%;P<0.001).The maternal complications rate of fetal distress,premature and the neonatal complications rate of fetal macrosomia,neonatal respiratory distress syndrome (NRDS),low weight,congenital heart disease,neonatal pneumonia,and rate in neonatal NICU were significantly lower than those in the control group (P<0.05).Conclusion:One-day outpatient intervention could control blood sugar effectively,reduce the maternal and neonatal complications.It is worth promoting.