Objective：To evaluate the diagnostic value of peripheral blood microRNA（miR）-21 and plasma poly（ADP - ribose） polymerase-1（PARP-1）in allergic rhinitis（AR）and combined allergic rhinitis and asthma syndrome（CARAS）. Methods：Peripheral blood samples were collected from 44 CARAS patients，31 AR patients，and 42 healthy controls. The expression levels of miR-21 in peripheral blood were detected by RT-qPCR，and the plasma levels of PARP-1 protein were measured by ELISA. Correlation analysis was performed by rearson correlation analysis. The diagnostic sensitivity and specificity of miR- 21 and PARP-1 were determined by receiver operating characteristic（ROC）curve. Results：The expression of peripheral blood miR - 21 was high in CARAS patients compared with healthy controls. The level of PARP - 1 was higher in AR patients than that in CARAS patients and healthy controls. Pearson correlation analysis showed that the expiression of miR - 21 was correlated with eosinophils count in AR patients and with fractional nasal nitric oxide（FnNO）in CARAS patients. The plasma level of PARP-1 was correlated with forced expiratory volume in one second percent predicted（FEV₁%_pred）in CARAS patients and with FEV₁%_pred and forced expiratory volume in one second（FEV₁）/forced vital capacity（FVC）（FEV₁/FVC）in CARAS patients. ROC curve analysis showed that when peripheral blood miR-21 was used as a diagnostic marker for CARAS，the sensitivity was 51.35% and the specificity was 80.95%. When the plasma PARP -1 was used as a diagnostic marker for AR，the sensitivity was 90.32% and the specificity was 54.76%. When the plasma PARP-1 was used as a diagnostic marker for the progression from AR to CARAS，the sensitivity was 45.45% and the specificity was 90.32% . Conclusion：There are differential expressions of miR -21 and PARP -1 in peripheral blood of patients with AR and CARAS. the peripheral bolld miR -21 can serve as a diagnostic biomarker for CARAS，while the plasma PARP-1 can serve as a diagnostic biomarker for AR and as a biomarker for the progression from AR to CARAS. This has significant value in identifying diagnostic and therapeutic targets for AR and CARAS.