This study was purposed to investigate the clinicopathological features of acute tumor lysis syndrome (ATLS) in elderly patients with malignant non-Hodgkin's lymphoma, so as to explore its diagnosis and treatments. 2 cases of ATLS in elderly patients with non-Hodgkin's lymphoma were retrospectively analyzed, including progress of tumor, the level of laboratory examination, clinical manifestation and response to treatments. Data regarding clinical and biochemical parameters were collected. The results indicated that the 2 patients with non-Hodgkin's lymphoma were found to have high tumor burden, and were sensitive to anti-tumor treatments, and had many promoting factors of ATLS. 1 patient displayed hyperkalemia, but another displayed hypokalemia. Both patients were given allopurinol, hydration and alkalization, and one was given dialysis. But both died because of disease deterioration. ATLS rarely occurred in patients who were treated by rituximab only. But the patients with high grade NHL and high tumor burden maybe develop ATLS during 1 - 4 days after given rituximab. In conclusion, ATLS is one of factors of death in patients with malignant lymphoma. The clinical manifestation is not typical, and the diagnosis mainly depends on laboratory examination parameters. Earlier judgment, prophylaxis and effective treatment are important for improving prognosis of elderly DLBCL-NHL.