Objective To investigate the correlation between serum vitamin D level and central precocious puberty(CPP)in girls.Methods A total of 103 girls(case group)with central precocious puberty from Ningbo Woman and Children's Hospital and 53 healthy girls(control group)from health check-ups in Ningbo Women and Children's Hospital were collected as subjects.The serum levels of 25-hydroxyvitamin D3[25(OH)D3]in the two groups were detected by chemiluminescence method.The weight and height of girls in the case group were measured.The serum levels of follicle-stimulating hormone(FSH)and its peak value,luteinizing hormone(LH)and its peak value,estradiol(E2),prolactin(PRL),human chorionic gonadotropin(HCG)and thyroid function were measured by radioimmunoassay.The peak value of LH/FSH was calculated.B ultrasound examination of uterine adnexa was completed to calculate uterine volume and bilateral ovarian volume.According to the results of serum 25-(OH)D3,girls in the case group were divided into normal vitamin D group and vitamin D deficiency group,and the differences of hormone levels,uterine and ovarian development between the two groups were compared.Results The serum level of 25-(OH)D3 in case group was lower than that in control group,and the vitamin D deficiency rate in case group was higher than that in control group,with statistical significance(P<0.05).The age of breast nodules in vitamin D deficiency group was lower than that in vitamin D normal group(P<0.05).There were no significant differences in body weight,height,body mass index(BMI),uterine volume and left ovarian volume between vitamin D normal group and vitamin D deficiency group(P>0.05),and the right ovarian volume in vitamin D deficiency group was significantly higher than that in vitamin D normal group(P<0.05).There were no significant differences in serum levels of FSH,LH,PRL,HCG,peak value of FSH and thyroid function between normal and deficient groups(P>0.05).The levels of E2,LH and LH/FSH in vitamin D deficiency group were significantly higher than those in vitamin D normal group(P<0.05);25-(OH)D3 was negatively correlated with LH/FSH peak(r=-0.197,P<0.05),but was not significantly correlated with thyroid function,FSH,LH,PRL,E2,HCG,FSH and LH peak(P>0.05).Conclusion Vitamin D deficiency is associated with central precocious puberty in girls.Vitamin D deficiency may lead to early onset of precocious puberty.Vitamin D deficiency may affect the hypothalamic-pituitary-gonadal axis function,resulting in changes in reproductive hormone indexes and consequent increase in ovarian volume in girls.