Objective To analyze the therapeutic effects of endoscopic retrograde cholangiopancreatography (ERCP) and percutaneous transhepatic cholangial drainage (PTCD) on elderly patients with acute obstructive suppurative cholangitis (AOSC), and the impact on serum alpha-glutathione S-transferase (alpha-GST) and bile inflammatory factors. Methods This study was a prospective study. A total of 120 elderly patients with AOSC who were admitted to the Xianyang First People's Hospital from January 2021 to April 2024 were assigned to observation group and control group using the random number table method, with 60 patients in each group. Observation group underwent ERCP and control group underwent PTCD. The two groups were compared in terms of the time to symptom relief, postoperative hospital stay, liver biochemical indicators ［serum direct bilirubin (DBIL), total bilirubin (TBIL), alanine aminotransferase (ALT) and aspartate aminotransferase (AST)］, serum alpha-GST and bile inflammatory factors ［interleukin-6 (IL-6), interleukin-10 (IL-10) and tumor necrosis factor-α (TNF-α)］. The incidence rates of postoperative complications were statistically analyzed.Results There was no significant difference in the time to abdominal pain, fever and jaundice relief between the two groups (P＞0.05). Postoperative hospital stay of observation group was significantly shorter than that of control group (P＜0.05). Serum DBIL, TBIL, ALT and AST levels in both groups on day 7 after operation were lower than preoperative levels (P＜0.05), but there was no significant difference between the groups (P＞0.05). Serum alpha-GST levels in both groups on day 7 after operation were lower than preoperative levels (P＜0.05), and serum alpha-GST level in observation group was lower than that in control group (P＜0.05). Compared with postoperative day 1, there were decreases in bile IL-6 and TNF-α levels, and increases in bile IL-10 levels in both groups on postoperative day 7(P＜0.05). Above indicators in observation group were better than those in control group (P＜0.05). The total incidence rates of postoperative complications in observation group and control group were 10.00% and 5.00%, without significant difference between the groups (P＞0.05). Conclusion Both ERCP and PTCD can promote clinical symptom relief and improve liver function in elderly patients with AOCS. However, ERCP has more advantages in lowering serum alpha-GST level and alleviating inflammatory reactions