Objective: To explore the impact of different body mass index (BMI) ranges of gestational diabetes mellitus (GDM) pregnant women with normal pre-pregnancy BMI on pregnancy outcomes. Methods: A retrospective collection of 2,319 cases of GDM pregnant women with normal pre-pregnancy BMI from May 2022 to May 2023 at Nanjing Maternal and Child Health Hospital. They were divided into Group A (18.5≤BMI<20 kg/m2, 581 cases), Group B (20≤BMI<22 kg/m2, 922 cases), and Group C (22≤BMI<24 kg/m2, 816 cases) according to pre-pregnancy BMI. Logistic regression was used to analyze and evaluate the association between different BMI levels and pregnancy outcomes. Results: The risk of GDM A2 level, preeclampsia, macrosomia, and neonatal hyperbilirubinemia in the three groups of GDM patients increased with the increase of pre-pregnancy BMI; the risk of placental abruption and neonatal hypoglycemia decreased with the increase of pre-pregnancy BMI. Conclusion: In the normal BMI population, higher or lower pre-pregnancy BMI levels in GDM women are independent risk factors for GDM A2 level, preeclampsia, macrosomia, neonatal hyperbilirubinemia, placental abruption, and neonatal hypoglycemia. Early weight management may be one of the key measures to prevent adverse pregnancy outcomes in GDM pregnant women.