The goal of this clinical trial is to learn if GR1802 works to treat severe chronic rhinosinusitis with nasal polyps (CRSwNP) in adults. It will also learn about the safety of GR1802. The main questions it aims to answer are: 1. Does GR1802 reduce the need for surgery and systemic corticosteroid use？ 2. What medical problems do participants have when taking GR1802? Researchers will compare GR1802 to a placebo (a look-alike substance that contains no drug) to see if GR1802 works to treat CRSwNP. Participants will: Take GR1802 or a placebo once every 2 weeks for 13months. Visit the clinic once every 2 weeks for checkups and tests. Keep a diary of their symptoms and the dosage and number of times they use mometasone furoate nasal spray.