The study is being conducted to evaluate the efficacy and safety of HR021618 in the treatment of moderate to severe pain after abdominal surgery.

Inclusion Criteria:

1. Able and willing to provide a written informed consent
2. Subjects requiring elective general anesthesia abdominal surgery
3. Male or female
4. Meet BMI standard
5. Conform to the ASA Physical Status Classification

Exclusion Criteria:

1. Subjects with a history of abdominal surgery
2. Subjects had hemorrhagic disorders
3. Subjects had cardiac, serious hepatic or renal, cardiovascular or cerebrovascular, metabolic, psychiatric disorders, chronic pain, or malignant tumors
4. Subjects with poor blood pressure control after medication
5. Abnormal QTc
6. Abnormal random blood glucose
7. Abnormal values in the laboratory
8. Allergic to meloxicam or any excipient of HR021618, aspirin, other non-steroidal anti-inflammatory drugs (NSAIDs) or to any peri- or postoperative medications used in this study
9. Use other drugs that affect the analgesic effect before randomization, and the time from the last use to randomization is shorter than 5 half-lives
10. Pregnant or nursing women
11. No birth control during the specified period of time
12. Participated in clinical trials of other drugs (received experimental drugs)
13. The inestigators determined that other conditions were inappropriate for participation in this clinical trial