Objectives: Recent studies have shown that regulatory T cells(Treg) play a role in protecting the kidney and are the expected immunotherapy target in CKD. AST-120 adsorbs uremic toxins and excretes them in the feces. In animal experiments, it has been reported that administration of AST-120 reduces the severity of glomerulosclerosis and the level of serum creatinine and the rate of decline in renal function in animals with chronic kidney disease. This study was conducted to evaluate the effect of AST-120 on Treg distribution and renal function. Methods: This study included 27 adult patients diagnosed with CKD stages 3,4,5 at Kosin University Gospel Hospital from March to December 2020. Complete blood count, creatinine (Cr), sodium, potassium, albumin, and total CO2 were included in the laboratory findings. For patients with chronic kidney disease stage 3, 4, and 5 who have been taking AST-120 for less than 1 month, These clinical and laboratory data were collected at the initiation of the study and after 3 months . Tregs were defined as CD4+CD25highCD127low/-FoxP3+ cells. Results: The patient group with a glomerular filtration rate of less than 30 mL/min showed less decrease in renal function and a higher distribution of regulatory T cells compared to the group with a glomerular filtration rate of 30 or higher. Conclusions: In CKD patients, taking AST-120 may help improve renal function by excreting uremic toxins from the body, thereby reducing immune dysfunction caused by uremic poisoning.