Objective：This study aims to investigate the relationship between D-dimer in different periods and postoperative deep venous thrombosis(DVT)in patients with early gastric cancer and premalignant lesions underwent endoscopic submucosal dissection (ESD). Methods：A retrospective cohort study was carried out，176 patients with early gastric cancer were collected，including 117 men with an average age of(62.9±9.7)years. According to the results of vascular ultrasound examination of the lower extremities at 3 days after surgery，the patients were divided into two groups：venous thrombosis group(12 people)and non -venous thrombosis group (164 people). General clinical data of patients were collected. Postoperative DVT risk score was calculated by Padua scale. The blood D -dimer level of all patients were measured 1 day before operation，immediately after operation and 1 day after operation. The ROC curve and area under curve(AUC)of multiple variables were analyzed to predict DVT after ESD. The relationship between D -dimer level and DVT after ESD was analyzed by multiple regression model. Results：There were 176 patients underwent vascular ultrasound examination of lower extremities 3 days after surgery，and 12 patients(6.82%)had lower extremity DVT. There was statistical significance in D-dimer levels between the two groups before ESD and 1 day after ESD(all P ＜ 0.05). The sensitivity，specificity and AUC of D - dimer 1 day after ESD to predicted DVT were 91.7%，67.1%，0.841(95% CI：0.778~0.892). Multivariate regression analysis showed that the level of D-dimer 1 day after ESD was significantly correlated with the increased risk of DVT after ESD(OR：82.756，95% CI：6.000~1 141.349，P ＜ 0.001). Conclusion：The increased level of D - dimer 1 day after ESD is associated with an increased risk of DVT in patients with early gastric cancer and premalignant lesions underwent ESD.