The goal of this clinical trial is to compare the efficacy and safety of a single plastic stent versus a fully covered self-expanded metal stent in relieving benign biliary stricture secondary to chronic pancreatitis. The main questions it aims to answer is:

Whether the efficacy of a single plastic stent is non-inferior to that of a fully covered metal stent in patients with benign biliary stricture secondary to chronic pancreatitis？

Participants will be randomly assigned to receive either a single plastic stent (SPS) placement or fully covered self-expanded metal stent placement treatment for 6 months, and they will be followed up for 18 months.

Although a number of previous studies have shown that the drainage and dilation effect of a single plastic stent is limited for benign biliary stricture (BBS) secondary to chronic pancreatitis (CP), the poor management of CP itself in most studies may explain the unsatisfactory efficacy of a single biliary plastic stent in relieving CP secondary BBS. Investigators believe that the effective management of CP is an important step to solve the BBS secondary to CP, especially the effective removal of pancreatic duct stones, the relief of pancreatic duct obstruction and the maintenance of pancreatic duct patency. Previous data showed that in CP patients treated with ESWL combined with ERCP, 72.4% could achieve complete removal of main pancreatic duct stones and 90.8% could achieve successful endoscopic decompression. Under the premise of effectively removing the stones of the main pancreatic duct at the head of the pancreas and maintaining the patency of the pancreatic duct, using a single plastic stent for stent drainage of BBS is effective, and a single plastic stent has potential advantages such as lower stent displacement rate and cheaper. Therefore, investigators design a single-center, prospective, open-label, randomized controlled, non-inferiority trial to compare the effectiveness, safety, and cost-effectiveness of a single plastic stent and fcSEMS for the removal of CP secondary BBS under the premise that the primary disease, i.e. CP itself, was effectively managed.

Inclusion Criteria:

1. Age 18 or older;
2. Patients diagnosed with CP;
3. Symptomatic biliary stricture documented at time of enrollment for naïve stricture or at the time of prior plastic stent placement in strictures that had 1 prior plastic stent inserted: cholangitis, and/or an increase in total bilirubin or alkaline phosphatase levels(> 2 times the upper limit of normal) for more than 4 weeks;
4. Confirmation of bile duct stricture by imaging assessment.

Exclusion Criteria:

1. Prior plastic stenting exceeding six months or any metal stenting;
2. Incomplete removal of stones from the main pancreatic duct located in the head of the pancreas during ERCP procedures;
3. Biliary stricture of benign etiology other than chronic pancreatitis;
4. Developing obstructive biliary symptoms associated with an attack of acute pancreatitis;
5. Stricture within 2 cm of common bile duct bifurcation;
6. Biliary stricture of malignant etiology;
7. Patients with acute or chronic hepatitis, cirrhosis, primary sclerosing cholangitis, congenital biliary malformations or biliary fistula;
8. Symptomatic duodenal stenosis (with gastric stasis);
9. Subjects for whom endoscopic techniques are contraindicated;
10. Pregnancy, incarceration;
11. Life expectancy < 1 year;
12. Other conditions that inappropriate to participant in the study.