This is a multicenter, randomized, double-blind, placebo-controlled Phase II clinical trial. The study plans to enroll 210 adult patients with alcohol use disorder. After signing the informed consent form and undergoing screening based on inclusion/exclusion criteria, eligible participants will be randomly assigned to the low-dose group (naltrexone implant 0.9 g + general supportive psychological counseling), high-dose group (naltrexone implant 1.5 g + general supportive psychological counseling), and control group (placebo + general supportive psychological counseling) in a 1:1:1 ratio. On Day 0, participants will receive a single subcutaneous abdominal incision implantation with either 0.9 g or 1.5 g of naltrexone implant or placebo. Efficacy assessment will follow up to 24 weeks after randomization/dosing, while safety assessment will follow up to 48 weeks. There will be a total of 13 follow-up visits. Except for Day 3 (Visit 3) and Week 36 (Visit 12), which are telephone follow-ups, all other visits will be outpatient follow-ups. The first 24 weeks of the study will be double-blind. After completing the Week 24 follow-up, all participants will undergo efficacy assessment. Then they will enter the open-label observation period, followed up until Week 48.