Objective：To investigate the clinicopathocogical features, diagnosis and treatment of thyroid microcarcinoma (TMC) accidentally found in patients with nodular goiter during surgery. Methods：The clinical data retrospective analyses was conducted in 68 cases of accidental TMC during operation for nodular goiters from Jan. 2004 to Jan. 2010. Results：In all the cases, the largest benign nodules had an average diameter of (1.89±0.68) cm. The diameter of TMC was 0.1-0.8 cm with average (0.38±0.14)cm，in which the nodule diameter ≤0.5 cm was found in 43 cases (63.24%). Six cases (8.82%) were multifocal (1-4 centers), 62 cases（91.18%）were unifocal. Fonty-seven cases (69.12%) were diagnosed as TMC by rapid frozen section during surgery and underwent Ⅵ lymph node dissection. Other 21 cases (30.88%) had missed diagnosis during surgery, but was diagnosed as TMC by postoperative patholgy and did not undergo a second surgery for additional lymph node clearance. All the patients were followed up for 12-84 (average 52.47±13.26) months, and no recurrence or metastasis was found. Conclusions：Thyroid microcarcinoma is often discovered accidentally in patients with nodular goiter undergoing operation. Its preoperative diagnosis is difficult, but the prognosis is always favorable. For nodular goiter, wider surgical indication and larger resection extent is recommended.