Objective:Application of the Bethesda system (TBS)for reporting thyroid cytology in fine needle aspiration(FNA)to improve the capability of cytopathological diagnosis. Methods:Totally 1 705 FNA cytopathological samples were analyzed from May 2011 to Jun 2012. Sixty-six histological pathological samples from these patients were analyzed in the meantime. Results:According to TBS,1 705 FNA cytopathological samples were classified into six categories with 295(17.30%)as nondiagnostic(N),1 291(75.72%)as benign(B),30(1.76%)as atypia of undetermined significance(AUS),19(1.11%)as follicular neoplasm(FN),36(2.11%)as suspicious(S)and 34(1.99%)as malignant(M). Total positive cell rate was 82.70%. It was concluded from the comparison of histopathological and cytopathological slides of 66 patients that the overall occurrence rate of malignancy was 11.11% in former two groups,which was significantly lower than that (63.33%) in latter four groups (P < 0.01). The sensitivity,specificity,positive predictive value,negative predictive value,false positive rate and false negative rate for FNA in differentiation of benign and malignant lesions were calculated as 82.61%,74.42%,63.33%,88.89%,25.58% and 17.39%, respectively. Conclusion:TBS showed great importance in differentiation of benign and malignant thyroid lesions,with high probability of malignancy in AUS,FN,S and M groups.