Abstract: Objective To investigate the changes of serum 25-hydroxyvitamin D ［25(OH)D］ in patients with hypertension during pregnancy and its clinical significance. Methods A total of 280 mid-to-late pregnant women who underwent birth check-up were selected as study subjects, and were divided into sufficient group(n=78), mild deficiency group(n=85), moderate deficiency group(n=62), severe deficiency group(n=55)according to 25(OH)D levels in prenatal check-up. Comparison of the incidence of pregnancy-induced hypertension in each group was performed. Meanwhile, based on the diagnosis and follow-up results, these patients were divided into normal pregnancy group(n=125)and observation group(n=155)that were further subdivided into pregnancy-induced hypertension group(n=86), mild preeclampsia group(n=34), severe preeclampsia group(n=17), chronic hypertension complicated with preeclampsia group(n=18)according to the types of disease. The serum 25(OH)D levels of normal pregnant group, observation group and their subgroups were compared, and the relationship between serum 25(OH)D level and pregnancy-induced hypertension was analyzed. Results The incidence of pregnancy-induced hypertension was the highest in severe deficiency group(100.0%), followed by moderate deficiency group, mild deficiency group and adequate group. The level of serum 25(OH)D in normal pregnant women was significantly - higher than that in subgroups(P<0.05), and was the lowest in chronic hypertension complicated with preeclampsia group. Conclusion Serum 25(OH)D level is significantly related to pregnancy-induced hypertension, and timely guidance of vitamin D supplementation for pregnant women is of great significance in the prevention of pregnancy-induced hypertension.