Objective This study was to investigate the lymph node metastasis pattern in thoracic esophageal squamous cell carcinoma (ESCC),and analyze the risk factors to provide reference for the delineation of radiotherapy target.Methods A total of 319 patients with thoracic ESCC who underwent surgical treatment at the second hospital of Dalian medical university were analyzed retrospectively.The lymph nodes around esophageal were divided into 20 groups according to the mapping scheme of the American Thoracic Society (ATS) modified by Casson et al.Analyzed the pattern of lymph node metastasis and its relationship with tumor location,tumor length,depth of invasion,pathological grade,and vessel invasion.Results The lymph node metastatic rate was 48.90％ (156/319),while the metastatic ratio of lymph node (LMR) was 15.70％ (562/3 581).The lymph node metastatic rates had gradually increasing trend with tumor sites descending (upper ESCC 35.48％,middle ESCC 47.06％ and lower ESCC 56.43％),but no statistically significance (P ＞ 0.05) was observed.In the whole 20 groups,the higher node metastasis stations of upper thoracic ESCC LMR were 1,2,4,5,7,9 (x2 =27.38,P ＜ 0.05),while the middle thoracic ESCC LMR were 2,4,5,7,8M (x2 =57.77,P ＜ 0.05),and the lower thoracic ESCC LMR were 4,5,7,8L,16,17,20 (x2 =28.88,P ＜ 0.05),with statistically significance.So the main lymph node metastasis stations were paraesophageal nodes,tracheobronchial nodes,paratracheal nodes,aroticopumonary nodes,left gastric nodes,subcarinalnodes and celiac nodes.The univariate analysis revealed that lymph node metastasis was correlated with the tumor length,depth of invasion,pathological grade,and presence of vascular invasion (x2 =6.82,26.04,36.26,4.56respectivcly,P ＜ 0.05).The muhi-variate regression analysis showed that tumor length and depth of tumor invasion were independent risk factors for lymph node metastasis (OR =2.212,2.123,P ＜ 0.05).Conclusions The factors influencing lymph node metastasis in thoracic ESCC include tumor length,depth of invasion,pathological grade,and presence of vascular invasion,which should be carefully considered during the target delineation of radiotherapy for esophageal carcinoma.