The goal of this clinical trial is to learn if inverted-Ω anastomosis after pancreatic head resection or mid-pancreatectomy works in benign or low-grade malignant tumor. It will also learn about the safety and feasibility of inverted-Ω anastomosis. The main questions it aims to answer are:

1. Does inverted-Ω anastomosis operate safely? (operative time, blood loss, transfusion and conversion rate)
2. What is the incidence and severity of postoperative complications in inverted -Ω anastomosis? What advantages does it have over conventional anastomosis methods such as roux-en-y？

Inclusion Criteria:

1. Age 18 to 75 years old, gender not limited;
2. Patients diagnosed with benign or low-grade malignant tumors in the head or middle section of the pancreas by CT or MRI;
3. ECOG score 0-1.

Exclusion Criteria:

1. Those with severe heart, liver or kidney insufficiency, or those who are assessed as intolerant to surgery or anesthesia, or those with ASA grade > 3;
2. Patients with a history of or concurrent other malignant tumors, or other serious infections or infectious diseases, or those who are unable to complete the anastomosis surgery;
3. Uncontrollable concomitant diseases, including but not limited to severe coronary artery disease, COPD or asthma, uncontrollable cerebrovascular diseases, symptomatic congestive failure, unstable angina pectoris, arrhythmia, or other diseases that the researchers consider ineligible for enrollment;
4. Patients who have undergone other upper abdominal surgeries and digestive tract reconstruction procedures in the past;
5. Patients requiring combined organ resection;
6. Preoperative assessment suggested that the patient might have factors such as active ulcers and bleeding in the digestive tract;
7. Pregnant and lactating women;
8. Any uncertain factors that have an impact on the patient's safety or compliance.