Objective To investigate the influence of preoperative thyroid fine needle aspiration cytology(FNAC) on the category of thyroid diseases after surgery. Methods This study included 11574 thyroid surgery cases in West China Hospital from 2007 to 2016. The total number of thyroid surgery cases, preoperative FNAC cases and intraoperative freezing cases were calculated year by year. According to the postoperative pathology, the proportion of benign and malignant lesions and the proportion of different malignant types, including papillary thyroid microcarcinoma(PMTC) were also calculated per year. The association between the development of FNAC and the percentage of malignant types changes were also calculated. Results The percentage of preoperative FNAC increased from 2.24% to 72.30% with the decrease of intraoperative freezing rate from 85.39% to 47.50%. The proportion of postoperative malignant tumors increased from 25.93% to 83.86%, with papillary thyroid carcinoma （PTC） increased from 86.21% to 97.53% and PMTC increased from 21.33% to 47.64%. Moreover, medullary cancer decreased from 2.87% to 1.21% and follicular cancer decreased from 7.47% to 0.57%. The undifferentiated/poorly differentiated cancers were only 28 cases during ten years. Conclusion The percentage of malignant thyroid tumors was significantly increased with the development of thyroid FNAC, which greatly changed the composition of malignant tumors and reduced the pressure of intraoperative freezing. Therefore, we concluded that FNAC before surgery was worth promotion in the future clinical practice.