Objective:To investigate the expression levels of serum calcitonin (CT) and osteoponin (OPN) in peripheral blood of patients with atrial fibrillation (AF) and their relationship with AF.Methods:A case control study was conducted, 160 AF patients treated in Shaanxi Provincial People's Hospital from June 2020 to December 2021 were selected as case group, and 160 healthy people in the same period were selected as control group. The expression levels of serum CT and OPN in the two groups were analyzed retrospectively, and the correlation between them and AF was analyzed. The value of CT and OPN levels in predicting the occurrence of AF was analyzed by receiver operating characteristic (ROC). Kappa consistency test was used to analyze the efficacy of the combination of them in predicting the occurrence of AF.Results:The serum calcitonin level ((13.5±3.2) ng/L) in the case group was lower than that in the control group ((17.3±3.1) ng/L), and the osteopontin level ((53.8±8.2) μg/L) was higher than that of the control group ((44.1±6.8) μg/L), the difference between the two groups was statistically significant ( t=10.79, P<0.001; t=11.50, P<0.001). The results of binary logistic regression analysis showed that serum calcitonin was the protective factor of atrial fibrillation ( OR=0.723, 95% CI: 0.661-0.790, P<0.001), and osteopontin was the risk factor ( OR=1.183, 95% CI: 1.131-1.237, P<0.001). ROC analysis showed that the area under curve (AUC) of CT, OPN and their combination in predicting AF were 0.794, 0.824, and 0.892, respectively. The predictive critical value for serum CT was <15.0 ng/L and >48.5 μg/L for OPN. The sensitivity, specificity of the combination in AF prediction were 67.50% and 93.75% respectively, and Kappa value was 0.613. Conclusion:The expression of serum CT and OPN was abnormal in patients with atrial fibrillation. The prediction of AF by combined examination of the two had a high degree of consistency with the actual results, which could provide reference for early diagnosis and treatment of AF. However, the rate of missed diagnosis was relatively high, which needs attention in clinical application.