To investigate the expression of 25-hydroxyvitamin D［25(OH)D］, mean platelet volume (MPV), and homocysteine (Hcy) of women with hypertensive disorder complicating pregnancy, and to study their relationship with the disease severity. Methods: 80 women with hypertensive disorder complicating pregnancy were selected in study group from June 2017 to June 2019. 80 healthy pregnant women were selectedin control group during the same period. The blood levels of of 25-(OH) D, MPV and Hcy of women in the two groups were detected. The influencing factors of the occurense and the disease severity of hypertensive disorder were analyzed. Results: The level of blood 25-(OH)D of women in the study group was significant lower than that of women in the control group, but the levels of MPV and Hcy of women in the study group were significant higher (P<0.05). In the study group, the level of blood 25-(OH) D of women had gradually decreased with the severity of the disease, but the levels of MPV and Hcy had gradually increased (P<0.05). Logistic regression analysis showed that the levels of blood 25-(OH) D, MPV and Hcy were the risk factors for the development and the severity of hypertensive disorder complicating pregnancy. Spearman correlation analysis revealed the expression of blood 25-(OH) D was negatively correlated with the severity of hypertensive disorder complicating pregnancy (r1=-0.762), but the expression of MPV and Hcy was positively correlated with the severity of hypertensive disorder complicating pregnancy (r2=0.506, r3=0.794, P<0.05). Conclusion: In pregnant women with hypertensive disorder complicating pregnancy, the level of blood 25 (OH) D is low, and the levels of MPV and Hcy are high, which are closely related to their disease severity, so they can provide evidence for clinical diagnosis and treatment.