Abstract： Objective To investigate the effects of 25-hydroxyvitanim[25(OH)D3],low density lipoprotein cholesterol(LDL-C)and homocysteine(HCY)on the stability of carotid plaque in Hashimoto's thyroiditis patients with normal thyroid function.Method A total of 200 patients diagnosed with Hashimoto's thyroiditis complicated with carotid artery plaque underwent physical examination in People's Hospital of Inner Mongolia Autonomous Region from January 2021 to April 2023 were selected,and 116 normal population were randomly selected as the control group.The patients with Hashimoto's thyroiditis complicated with carotid plaque were divided into stable plaque group(n=132)and vulnerable plaque group(n=68)according to the characteristics of plaque thickness,internal echo,ultramicro blood flow,ulceration and fibrous cap integrity.The basline data of the three groups of patients were recorded,the stability of carotid plaque was assessed by receiver operator characteristic(ROC)curve,the area under curve(AUC)of ROC was calculated.Result The levels of glucose(GLU),total cholesterol(TC),LDL-C,and HCY in the stable plaque group and vulnerable plaque group were higher than those in the control group,while the levels of 25(OH)D3 and high-density lipoprotein cholesterol(HDL-C)were lower than those in the control group,the differences were statistically significant(P<0.05).The differences in LDL-C and HCY between the stable plaque group and the vulnerable plaque group were statistically significant(P<0.05).The results of multivariate analysis showed that LDL-C and HCY were independent risk factors for the development of vulnerable plaques in the carotid artery(P<0.05).ROC curve analysis showed that the AUC of LDL-C and HCY for diagnosing vulnerable carotid plaques were 0.662 and 0.633,respectively,with sensitivities of 0.706 and 0.824,specificities of 0.636 and 0.273,respectively.Conclusion 25(OH)D3,LDL-C,HCY,GLU,TC,and HDL-C are all influencing factors for the formation of carotid plaques in patients with Hashimoto's thyroiditis.LDL-C and HCY are independent risk factors affecting the stability of carotid plaques and have predictive value for vulnerable carotid plaques.