Objective: To explore the effects of insulin intervention timing on blood glucose control level, cervical local microcirculation level and maternal and infant outcomes in patients with gestational diabetes mellitus. Methods: A total of 98 patients with gestational diabetes mellitus in our department from January 2022 to January 2024 were selected as the study objects, and were divided into the late group (49 patients with gestational age >32 weeks) and the early group (49 patients with gestational age ≤ 32 weeks) according to the time of starting drug administration, all of whom received insulin treatment. Blood glucose control level, cervical local microcirculation level, insulin resistance and islet beta cell function changes, adverse delivery outcomes and neonatal complications were compared between the two groups. Results: After 2 weeks of treatment, the 2 h postprandial blood glucose, fasting blood glucose, 24 h average blood glucose fluctuation range and daytime average blood glucose fluctuation range were decreased in 2 groups (P<0.05), and lower in early group (P<0.05), and there was no significant difference in HBA1c between 2 groups (P>0.05). Capillary diameter, blood perfusion and microvascular tube diameter were increased in both groups (P<0.05), and higher in the early group (P<0.05). The insulin resistance index of the steady-state model was decreased in both groups, and was lower in the early group (P<0.05), and the islet β cell function index was decreased in both groups (P<0.05), and it was lower in the late group (P<0.05). The incidence of adverse delivery outcomes and neonatal complications in the early group were lower than those in the late group (P<0.05). Conclusion: Early insulin therapy can effectively control blood sugar, improve cervical local microcirculation, insulin resistance and islet beta cell function, and reduce adverse delivery outcomes and neonatal complications.