Objective To investigate the clinical value of apolipoprotein A1(apo A1)/apolipoprotein B(apo B)ratio and serum 25-hydroxyvitamin D [25(OH)D] in atherosclerosis(AS)complicated with osteoporosis(OP). Methods From January 2024 to May 2025,122 AS patients were enrolled from Xuanwu Hospital,Capital Medical University. The clinical data were collected,and routine biochemical indicators,bone turnover markers and 25(OH)D levels were determined. The patients were classified into 2 groups based on the presence or absence of OP,simple AS group(68 cases)and AS+OP group(54 cases). Logistic regression analysis was used to identify factors for OP. Pearson or Spearman correlation analysis was used to assess correlations among variables. Receiver operating characteristic(ROC)curves were used to evaluate the diagnostic performance of single and combined determinations for diagnosing OP in AS patients. Results In AS+OP group,blood glucose(Glu)and alkaline phosphatase(ALP)levels were higher than those in AS group(P<0.05),while apoA1,apo A1/apo B ratio,sodium,chloride and 25(OH)D levels were lower(P<0.01). No statistical significance was observed between the 2 groups regarding age,gender,triglyceride(TG),total cholesterol(TC),high-density lipoprotein cholesterol(HDL-C),low-density lipoprotein cholesterol(LDL-C),LDL-C/HDL-C ratio,apo B,total protein(TP),albumin(Alb),globulin(Glb),potassium,calcium,phosphorus,or collagen typeⅠcross-linked C-telopeptide(CTX)(P>0.05). Lower apo A1/apo B ratio and 25(OH)D levels were identified as risk factors for OP in AS patients [odds ratios(OR)were 0.444 and 0.915,95% confidence intervals(CI)0.215-0.919 and 0.852-0.984,P<0.05]. In AS patients,apo A1/apo B ratio and 25(OH)D showed positive correlations with OCN and CTX(P<0.01)and negative correlations with ALP(P<0.05). The areas under curves(AUC)for single determinations using apo A1/apo B ratio,25(OH)D,ALP,OCN,CTX and the combined determination of apo A1/apo B ratio+25(OH)D were 0.656,0.660,0.648,0.645,0.586 and 0.791,respectively. Conclusions Serum 25(OH)D and apo A1/apo B ratio are associated with OP in AS patients,and their combined determination may help screen high-risk individuals for AS-related OP.