This study aims to evaluate the efficacy and safety of parecoxib versus indomethacin in preventing post-endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis (PEP). It is a single-center, prospective, randomized, controlled, exploratory trial. Participants will be randomly assigned to receive either parecoxib or indomethacin as a preventive treatment. The primary endpoint is to compare the efficacy of the two drugs in reducing the incidence of PEP. Secondary endpoints include the incidence of moderate to severe PEP and post-ERCP-related adverse events. This study will systematically assess the efficacy and safety of both drugs, providing preliminary data for future larger confirmatory trials.