Objective: To investigate the effect of vitamin D deficiency on the levels of thyroid stimulating hormone (TSH), thyroid peroxidase antibody (TPO-Ab), interleukin-1 (IL-1) and high-sensitivity C-reactive protein (hs-CRP) in pregnant women with early pregnancy complicated by subclinical hypothyroidism. Methods: A total of 172 pregnant women with subclinical hypothyroidism in the first trimester diagnosed and treated in a given hospital from August 2014 to May 2018 were selected, and their levels of vitamin D were determined. Depending on the abnormality of their vitamin D levels, the study participants were divided into two groups: the study group (vitamin D <= 20 ng/L) and the control group (vitamin D>20 ng/L). The levels of TSH, TPO-Ab, IL-1 and hsCRP in the two groups were measured. Results: The levels of TSH, hsCRP and TPO-Ab in the study group were significantly higher than those in the control group (P<0.05). The comparison between the two groups in terms of IL-1 showed no statistically significant difference. Conclusion: Vitamin D deficiency in the first trimester is associated with in an increased level of TSH in the first trimester, thereby aggravating subclinical hypothyroidism. The mechanism may be associated with the impact of vitamin D deficiency on hs-CRP and other body inflammation indicators, as well as on thyroid autoantibodies and other immune indicators, but has no effect on IL-1 levels.