Objective To observe the effect of gestational weight gain (GWG) on glucose metabolism and pregnancy outcomes in patients with gestational diabetes mellitus (GDM). Methods The clinical data of 1667 single pregnant women with GDM diagnosed in the Department of Obstetrics and Gynecology of the Sixth Medical Center of Chinese PLA General Hospital from January 2019 to December 2021 were collected and retrospectively analyzed. According to the degree of GWG, all the GDM pregnant women were divided into three groups: little weight gain group (n=882), moderate weight gain group (n=566)and excessive weight gain group (n=219). The levels of glycosylated hemoglobin (HbA_1c), fasting plasma glucose (FPG), fasting insulin (FIN), Homeostatic Model Assessment of Insulin Resistance (HOMA-IR), homeostasis model assessment β cell function(HOMA-β) and neonatal birth weight were compared among the three groups. Logistic regression was used to analyze the correlation between GWG and adverse pregnancy outcomes. Results The levels of HbA_1c, FPG, FIN, HOMA-IR and HOMA-β in excessive weight gain group were significantly higher than those in little weight gain group and moderate weight gain group (P<0.05),and the levels of FIN, HOMA-IR and HOMA-β in little weight gain group were significantly lower than those in moderate weight gain group (P<0.05). The neonatal birth weight in excessive weight gain group was significantly higher than that in little weight gain group and moderate weight gain group (P<0.05), and the neonatal birth weight in little weight gain group was significantly lower than that in moderate weight gain group (P<0.05). Logistic regression analysis showed that both excessive weight gain and little weight gain were independent factors of hypertensive disorders of pregnancy (HDP), macrosomia and large for gestational age (LGA)(P<0.05). Conclusion Irrational weight gain during pregnancy may increase the incidence of glucose metabolism disorders and adverse pregnancy outcomes in pregnant women with GDM.