This study aimed to investigate the intake of dairy products during pregnancy in women with gestational diabetes mellitus (GDM), and its impacts on neonatal birth weight and pregnancy outcomes. A total of 386 women with GDM during the second trimester pregnancy participated in this prospective cohort study. We evaluated dairy products intake through Food Frequency Questionnaire. Pregnancy outcomes were obtained from the delivery data. Participants were divided into insufficient and sufficient intake of milk and dairy products group (<300 g/day and ≥300 g/day, respectively). The average intake of dairy products during the second trimester pregnancy in women with GDM was 317.8±179.5 g/day, and the total energy intake was 1635.4±708.7 kcal/day. However, 76.68% of them did not meet the recommended total energy intake of women with GDM. After adjusting for confounding factors, women with GDM who consumed ≥300 g/day of dairy products had an average reduction in birth weight of 93.1 g compared to women who consumed <300 g/day of dairy products (95% CI: -171.343, -14.927). Women with GDM in sufficient intake group was also associated with lower risk of macrosomia (95% CI: 0.043, 0.695) and cesarean section (95% CI: 0.387, 0.933), and not related to low birth weight infant (95% CI: 0.617, 14.502) and preterm birth (95% CI: 0.186, 1.510) when compared with participants in insufficient intake group. Under the premise of insufficient total energy intake, the intake of dairy products during the second trimester pregnancy in women with GDM might be related to the decrease of neonatal birth weight.