Background In recent years, with the development of imaging technology, the accurate diagnosis of precancerous lesions of digestive system and early lymphoma has attracted wide attention in the medical field. Methods In this study, 82 patients with gastrointestinal diseases, including 32 patients with early gastrointestinal lymphoma and 50 patients with gastrointestinal precancerous lesions, underwent dynamic contrast-enhanced computed tomography (CT) scanning. The difference ( δ 1, δ 2) and ratio ( Q1 , Q2 ) of density between arterial phase, portal phase and plain scan were measured and compared, and the receiver operating characteristic (ROC) curve of the subjects was drawn. Results The results showed no statistically significant differences in the general condition of patients or a difference for the results of the arterial phase δ 1 and Q1 between the two groups (P>0.05). However, the portal venous phase δ 2 and Q2 in the early lymphoma group and in precancerous lesion group were 29.50±6.05, 41.55±10.10 Hounsfield units (HU), and 1.70±0.05, 2.06±0.31, respectively. The area under the ROC curve (AUC) values for δ 2 and Q2 to identify the two diseases were 0.755 and 0.878, respectively. When δ 2 and Q2 were 35.63 and 1.86 HU, the specificity was 89.60% and 67.50%, and sensitivity was 89.60% and 64.90%, respectively. When the two indexes, δ 2 and Q2 , were combined, the specificity and sensitivity of diagnosis were 98.99% and 56.80%, respectively. Conclusions Dynamic contrast-enhanced CT can effectively distinguish early gastrointestinal lymphoma from precancerous lesions and improve the diagnostic accuracy.