Abstract: Objective: To evaluate correlation factors of lymphatic metastasis (LM) in thoracic esophageal carcinoma and to examine the clinical significance of the number of metastatic lymph nodes (NMLN). Methods: Research on clinicopathological data of 1,146 patients, who had undergone simple resection of squamous cell carcinoma of the thoracic esophagus, was performed using Kaplan- Meier survival curves and Spearmam correlation analysis. Results: LM was found in 380 of the 1146 cases with esophageal carcinoma (33.2%), and in the 4,270 excised lymph nodes, metastases can be seen in 807 (18.9%). The LM rate was 0.0%, 20.0%, 25.7%, 37.3% and 50.0% for the depth of tumor invasion (T) of Tis, T1, T2, T3 and T4 (P<0.001) and the LM rate tumors of length less than 3 cm, 3 to 5 cm,5.1 to 7 cm and more than 7 cm was 12.8%, 29.6%, 37.3% and 46.8%, respectively (P<0.001). The LM rate was 32.4% in the well and moderately differentiated cells and 48.2% in the poorly differentiated cells. There was a statistical difference among the effects of the above 3 factors on the LM, but no obvious statistical significance was found among sex, age, tumor site or pathomorphological typing to affect LM. The 5- year survival rate for the cases with the NMLN of 0, 1 and more than or equal to 2 was 59.79%, 33.38% and 9.35%, respectively. There was a significant difference among the survival of the 3 groups (P<0.01). Conclusion: The major influential factors of LM in squamous cell carcinoma of the thoracic esophagus are the depth of tumor invasion, the tumor length and the cellular differentiation of the tumor. The NMLN can reflect the prognosis of patients undergoing surgery for squamous cell thoracic esophageal carcinoma.