Objectives: To investigate the evaluation of bone mineral density (BMD) in patients with gestational diabetes mellitus (GDM) by ultrasonic bone mineral density measurement combined with Vitamin-D deficiency and its influencing factors. Methods: A total of 100 patients with gestational diabetes mellitus (GDM) admitted to our hospital from January 2017 to December 2020 were selected as the GDM group, and another 100 pregnant volunteers who underwent physical examination in our hospital were selected as the healthy control group. The levels of triacylglycerol (TG), total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), glycated hemoglobin (HbA1c), fasting insulin (FINS), C-peptide, procollagen, parathyroid hormone (PTH), serum calcium, 25-hydroxyvitamin-D3 (25-OH-D) and ultrasonic BMD Z-score were determined and compared between the two groups. Moreover, the effects of different levels of 25-OH-D on the above indexes were compared, and multivariate logistic regression analysis was performed. Results: Compared with the healthy reference group, the levels of TG, TC, LDL-C, PTH, HbA1c, FINS and C-peptide of GDM group were significantly increased (P < 0.05), while BMD Z-score and 25-OH-D levels were significantly decreased. In the GDM group, the lower the 25-OH-D levels, the higher the FPG, HbA1c and FINS levels and the lower the serum calcium level and BMD Z-score, with statistically significant differences (P < 0.05). Multivariate logistic regression analysis showed that 25-OH-D was an independent risk factor affecting BMD in patients with GDM (P<0.05). Conclusions: Patients with GDM have lower BMD and 25-hydroxyVitamin-D3 levels. Measurement of BMD and 25-hydroxyVitamin-D3 levels can help assess the progression of GDM. BMD has a close bearing on Vitamin-D deficiency in patients with GDM.